I use VirtualBox to run Ubuntu 32-bit and various other Linux distros on Win7 64-bit. No Truecrypt or Dropbox is involved. I have similar occasional issues with shared folders.
Access denied randomly when trying to overwrite files. Files renamed in the host becoming inaccessible from the guest. NTFS symlinks in the host appearing as normal folders in the guest one day and as broken links the next day. Terribly slow I/O overall. I used to bookmark and keep track of several bug reports on the official bugtracker, but I gave up because nobody seemed to care.
The only reason I still use shared folders is because it's still slightly less painful than CIFS/Samba.
Hm, I've seen some really weird unicode-related corruption hitting files shared between guest and host due to (I assume) different line ending convention. Figuring out what was going on was not fun at all.
Access denied randomly when trying to overwrite files. Files renamed in the host becoming inaccessible from the guest. NTFS symlinks in the host appearing as normal folders in the guest one day and as broken links the next day. Terribly slow I/O overall. I used to bookmark and keep track of several bug reports on the official bugtracker, but I gave up because nobody seemed to care.
The only reason I still use shared folders is because it's still slightly less painful than CIFS/Samba.