If you want to possibly avoid any keylogging you could try the following:
1) Put a portable browser on your flash drive, (not necessary but does come in handy),
2) Grab the source archive from here
and extract to the flash drive, (you can delete everything but the index.html and js, css folders),
3) When you want to decrypt, open the index.html, type in your password, then cut and paste into your encryption program.
Possibly also make sure the browser is running in privacy mode before doing it....and make sure no-one is peering over your shoulder