Take a look and see if there are any Poseray processes running (task manager).  I'm running xp 64 and I only see one process, Poseray.exe, so check that that one isn't still listed.  I haven't seen this problem with Poseray, but there are plenty of applications out there that don't shutdown properly.
Have you re-booted and tried it?  Did you make any driver changes lately?  And finally, maybe a re-install is necessary. 
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