The internal versioning of OSXFUSE has changed slightly in the new 2.6.4 release so our code for checking the OSXFUSE version did not work correctly anymore.
We have released a small update (v2.0.411.566) for Boxcryptor for OS X yesterday which correctly detects also the new versioning scheme and accepts OSXFUSE 2.6.4. You can download it here:
Regarding the original question for MS Office files: I'm sorry, but the new OSXFUSE version 2.6.4 does not yet fix this issue and the workaround to close Google Chrome while the Boxcryptor Disk is mounting still has to be applied. (We're one of the very few sponsors of the OSXFUSE project - which mainly consists of one developer with whom we're constantly in contact)