If you are not running 12.20 SR10, 12.30 SR4 or 12.40 SR3 updating to the current SR would be the first step I would recommend you taking on this to alleviate any prior issues that have already been fixed in the later SR... This may also be related to the web server component too, so I would check both the QVS and QVWS logs for clues too, you will want those logs to be in the High verbosity setting to get the most logging information, otherwise may not be very useful.
Regards, Brett
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