If a team server operation like updating or committing is interrupted or fails, the working copy (i.e. the checkout of the project on your disk) is still locked. To remedy this, you need to install TortoiseSVN 1.7.15 and then right-click your project folder and choose “TortoiseSVN > Clean up”. Make sure the checkbox “Clean up working copy status” is checked. And click OK. The working copy is now unlocked.
Now that I see such an error again, I’m going to try and build it into the Modeler so you do not need TortoiseSVN for this anymore.
Update: another answer suggests to use the “Release lock” option of TortoiseSVN. Confusingly, this is about a different kind of lock and is not useful in the described scenario.
i had the same problem. Did send a support request to Mendix. They are investigating the problem.
I was receiving this same message earlier this week and I had to download Tortoise SVN 1.7 again and use it to release any locks on the files in my Mendix project directory. Locate the directory of the Mendix project and right click the project and select Tortoise SVN and then select Release Lock. Hopefully this works.