File is checked out or locked for editing by someone else

After upgrading some workstations to Windows 7 / 64b, users started having problems while saving big Excels. Sometimes when they open up a big Excel they get an empty error dialog window.

After editing and trying to save the document they get the following of 2 errors, they change from time to time, but most of the time it is the “File is checked out or locked for editing by someone else” error.

I noticed the error only appearing with big Excel documents so after some trial and error I found out the erros started appearing when the file was > 50.000.000 bytes. I knew the default file upload size in SharePoint is 50 MB, but this is quite easy to change. Go to Central Administration -> Web Application General Settings. Select the Web Application you want to change, and you will see a textbox to specify the maximum upload size. Problem solved? Not. I should have known because users on WinXP systems weren’t experiencing the same problems, so it had to be something client side.

After some googling I found the following Microsoft KB: You receive a folder copy error message when you try to download a file that is larger than 50000000 bytes from a Web folder. It was a long shot because there was nothing about SharePoint in the KB, but I tried. And, to my surprise, after changing the registry setting, all worked fine! No more errors!