Vista - Files Upload access problem with VISTA

I have a web site where all our clients log in.
There is a Java Applet that scans a known directory for one to many files.
Each file is uploaded to a servlet and on confirmation of receipt, the
applet deletes the file so as not to repeat the execise next time.
Everything works fine for the last 6 years,
then VISTA causes a JAVA security exception on the file delete.
It is impractical to deny the clients use of Vista or to visit them all.
Any ideas for a zero deployment solution, please.

Thanks,
Steve

OOPS
Forgot to mention that the known directory is on the C: Drive (hard-drive)
of the web users PC and the files are being upload repeatedly on the Vista
client PC's, since they are never deleted.
Have since tried IE7 on an XP machine and it works ok, so can only presume
that it is Vista.