🚀 go-pugleaf

I've got an IBM AT clone that I've just put together
for myself & it all seems to work fine except that
every so often, after completing an application,
like Quicken, instead of getting back my DOS prompt,
I'll get the Invalid COMMAND.COM message, need to re-boot.
After rebooting, everything is fine again. I've checked
my hard disks & there are only two copies of COMMAND.COM,
one in root & one in DOS, & I've compared them & they are
identical. 

Any ideas on what might be causing this problem ?

-brad a.