We recently ran into this issue when attempting to access our site through the Content and Structure page on the main site.  This error presented itself when attempting to expand the tree for a particular site.  After clicking the plus sign and waiting for a while, the error message would appear just below the site name.  After receiving the error, attempting to expand any other site resulted in the immediate display of the message. Also, when trying to access the Content and Structure page from any site under the problem site, SharePoint would display the Error page with the very useful “An unknown error has occurred” message. This was a big problem for us because we needed to move items, lists, and sites. 

Solution:

Ultimately the problem was caused by the server timing out on the request.  Our system administrator changed the IIS timeout settings from 120 to 600 for an unrelated issue.  After the setting was changed we no longer encountered the error.  We made the change on a development server that was having the same issue, and this solved the problem there as well.

***UPDATE***

 While this initially solved the problem, the issue has again reared it’s ugly head.  It started appearing again somewhere around the time we upgraded to SP1.  I’m not sure if it’s related though.  It may just be a coincidence.  This has been a low priority for us for now since there are other issues with SP1 that we have been addressing.  I will post another update if/when we find a solution to the problem.

***Final Update***

After many conversations with Microsoft Support, we finally found the problem.  There was a list with a workflow that had somehow lost its association with the list.  We could not delete it using Workflow Settings on the list.  Luckily we were soon phasing out the list anyway, so I deleted and recreated it.  We now no longer have the problem with Content and Structure.

1.  Ensure that SharePoint's journaling feature has been enabled.
2. In SharePoint, create a Picture Library to store the report images.
3.  In SSRS, create and deploy the reports.
4. Create email subscriptions in SSRS for each of the reports to be emailed to the new picture library with an attachment in PNG format.
5. Set up the picture library with a category field. Specify category values for each of the unique report types coming into the library.  In our case we have four unique report types and four corresponding categories.
6. In order to preserve a history of the reports, we created a workflow to append the date to each report's file name to make each file unique. We outlined this process in an earlier blog post:  Change a Filename using a Workflow.  Do not finish the workflow yet.
7. In the workflow, add another step.
8. Create a branch in the workflow for each category.
9. Add a condition to “Compare <picture library> field” in each branch.
10. Set the field to Title or Name, change Equal to Contains, and specify a keyword in the filename that identifies the category.
11. Add an action to “Set Field in Current Item” to each of the branches.
12. Set the field to your category field, and set the value accordingly for each branch.
13. Click “Finish.”

We then created a Web Part page to display the images.  We added the picture library web part to the page four times and made the following modifications to each one:

1. In the drop-down for the web part, select Modify Web Part and make the following changes:
1. Change the name to reflect the report being displayed.
2. Click on “Edit the current view” and make the following changes:
1. Uncheck the checked fields and check the Preview field.
2. Order by the create date in descending order.
3. Set a filter on the category field equal to the appropriate category.
4. Change the Item Limit to 1. 
5. Click Ok.

1.       With the file open, click the Save button.

2.       Close the file without checking it in.

3.       In the document library click Upload.

4.       Navigate to Documents > SharePoint Drafts and select the saved file.  Click Open.

5.       Make sure the check box for “Add a new version to existing file” is selected.

6.       Modify the Title if necessary and click Check In.

This procedure updated the file, and we were then able to open any other file in the document library, save it, and check it in without any problems.

1.       Open the problem site in SPD

2.       In the Folder List navigate to _catalogs/fpdatasources

3.       Right-click fpdatasources and click the Security tab

4.       Click “Manage permissions using the browser.”

5.       Add the appropriate permissions.

You may have to refresh or restart SPD to see the change, but the Data Source Library should no longer be grayed out.

Through knowledge gained in training along with a lot of head scratching, we came up with a solution.  It may not be the best solution, but it works for us.

1.       Create a column in the target library, name it “Text Date” (or whatever you prefer), set it as single line of text, and calculate the value using the following expression:

=Text([Today], “yyyymmdd”) 

2.       Create a workflow.

3.       Give it a name and select the checkbox for “Automatically start this workflow when a new item is created.”

4.       Click Next.

5.       Add the Action to “Set Field in Current Item.”

6.       Click Field and select “Title.”

7.       Click Value, click the function button, and in the Field drop-down select “Name (for use in forms)”.  This will set the title as the current filename without the file extension.

8.       Add the Action to “Build Dynamic String.”

9.       Click “Dynamic String” and create it as follows using “Add Lookup” (Documents is the name of my target library):

     [%Documents:Title%]_[%Documents:Text Date%].[%Documents:Type%]

10.   Click “Variable: variable1″, “Create a new variable.” and give it a name.  I called mine “FileName”.

11.   Add the Action to “Set Field in Current Item” again.

12.   Click Field and select “Name (for use in forms).”

13.   Click Value, click the Function button, change the source to “Workflow Data”, and change the field to “Variable: FileName”.

14.   Click Finish.

Once the Title field has been used to build the FileName variable, it can be rebuilt using any method you see fit.  The “Text Date” field can also be calculated using any date format you wish, however special characters such as / and : cannot be used in a file name.