Quicken 2008 Premier won't back up to USB flash drive

I'm running Quicken 2008 Premier on an iMac G5 using Virtual PC.  I've
been using this arrangement for years now with no complaints, but in
the last few days suddenly Quicken won't back up files to my USB
flashdrive.  I've checked and the flash drive is not full; I've also
tried to back up to another USB drive withe same lack of results.
Quicken goes through the motions, but at the end I get an error
message that the file was not backed up.  The OS seems to recognize
the flashdrive, I can see the activity light on the flashdrive blink a
few times, but for some reason nothing is going through.
I also tried to back up files to a location on the computer itself.
That didn't work either.
Curiously, I can't seem to be able to download stock quotes or contact
the Quicken BillPay server either.
That piece of the puzzle: I'm in the process of upgrading from the G5
iMac to an Intel powered iMac so I can do away with Virtual PC.  A few
days ago I hooked up the two macs via firewire in order to migrate my
files from the old to the new computer. I'm wondering if I accidently
screw something up with the old Mac at the time.  Everything else on
the old G5 still works fine.

Any ideas?
Many tks,

Mark