I too had many problems getting the OFO option to work properly.
I checked out tech support and the newsgroups, tried all of the
upgrades, patches & suggestions to no avail. Everything looked
ilke it should work - but it didn't. Checked out the VNCSnapshot
Service and found it was loging in as a System Account. Changed
the service to log on as administrator, stopped & restarted the
VNCSnapshot service, and the errors went away. Hope this helps!

"Joe F" wrote:
>Running BE 7.3 bld 2575 with ofofix.exe and post2575.exe on an NT 4.0 Server
>SP5 Dell machine. The first backup (including OFO) of drive C: runs fine.
>Future attempts to backup drive C: produce "OFO: not enough disk space on
>the device running OFO to create or increment the static volume. ....."
>The backup in question is of a 6GB drive partitioned into three 2GB partitions.
>The C: partition has 1.2GB of the 2GB free. If the computer is restarted
>the first backup runs fine and all subsequent backups fail until the machine
>is restarted again.