No build has been triggered for days even though a change to the sources has been checked in.

This is the Perforce Polling Log:
Started on Feb 8, 2011 3:20:57 PM
Looking for changes...
Using node: twinpeaks-vm
Using remote perforce client: hudson-OE-HUBS-DW-TWINPEAKS-VM
[OE-HUBS-DW] $ "C:\Program Files\Perforce\p4" workspace -o hudson-OE-HUBS-DW-TWINPEAKS-VM
Saving modified client hudson-OE-HUBS-DW-TWINPEAKS-VM
[OE-HUBS-DW] $ "C:\Program Files\Perforce\p4" -s client -i
Last sync'd change was 663559
[OE-HUBS-DW] $ "C:\Program Files\Perforce\p4" counter change
[OE-HUBS-DW] $ "C:\Program Files\Perforce\p4" -s changes '"//depot/IT_Engineering/DIAL - New QC App/..."@663559,@673276'
No changes found.
Done. Took 1.2 sec
No changes

This is what I get on the slave server when I do a "p4 changes":
--------------
Z:\>p4 -u rolem -c hudson-OE-HUBS-DW-TWINPEAKS-VM -s changes "//depot/IT_Engineering/DIAL - New QC App/..."@663559,@673241
info: Change 665714 on 2011/02/03 by fmartin@lglt-fmartin 'Eliminate 'Customer Requests' i'
exit: 0

So Perforce reports that something has been checked in, but the Perforce plugin doesn't seem to be seeing it.

One other thing worth mentioning: We have checked "Use View Mask" in the Advanced button of Perforce settings. The View mask is:
"//depot/IT_Engineering/DIAL - New QC App/..."
and the "Use mask when polling" checkbox is checked.