Hello
Snowman
You cannot expect other users to be able to help you by just telling that you've got a problem without giving any additional info (other than BSPlayer's buildnumber and that you're not using ffdshow).
I can only suggest to maybe upgrade/downgrade codec-version(s)/filter(s); it maybe related to conflicting codec(s), videocard (drivers), videorendering selection, other utilities (perhaps unknowingly) used in parallel, general system capacity (hardware/software); if it really occurs after exactly same lapse of time, I would even suspect conflicts with screensaver (or energysaving) trying to step in.