Ran into this the other day. The fix was easy but the cause was curious.
Error
An error occurred during the processing of /corporate/CorporateDocuments/Forms/AllItems.aspx. The server block is not well formed.
The Reason
While I’m sure a number of scenarios can create this situation, in my case it was a matter of saving a PowerPoint Slideshow to the URL of the document library (and mistyping the address) – i.e. via WebDAV, PowerPoint thwacked the allitems.aspx page. It shouldn’t have been allowed to do that, but ultimately, I did it.
The Fix
Load your site in SharePoint Designer and find the file in question, for the library impacted. You should find that the file has a blue “!” icon next to it, indicating it has been modified/customized/unghosted. Right click and choose Reset to Site Definition and you should be back in business.
Thanks
You were spot on
Saved a bit of embarrassment for a newbe