Hello there. First off, thank you for providing the community with your "safe" on-screen-keyboard, it certainly plugs a hole many people aren't even aware of.
Unfortunately, as seems to have been discovered with other programs as well (Opera?), some applications won't work as "recipients" of SafeKeys drag/drop operation, in this case i'm talking about TrueCrypt. This is very unfortunate, as passwords to encrypted filesystems are obviously quite "valuable" and there is really no other option in TrueCrypt than to enter your keyphrase using an inherently unsafe keyboard. Now, i know it's definitely not your fault that the people programming TrueCrypt wrote their software the way they did, but maybe there'd be other ways to send a password to a target application than just drag and drop? A software similar to your's, called "mouse only keyboard" seems to use a sort of locked clipboard that cannot be read by keyloggers monitoring your clipboard, maybe this could be an alternative?