I"d guess it"d be a memory problem.
I never have any problems with iPoker, and i use it regularly. My laptop has 2GB of RAM, which is obviously plenty. If you"re using something like PokerTracker, and have far less RAM, and running other applications at the same time then I"ve seen computers hang for a few moments. This is going to result in a disconnection or lag from the poker room.
As Jon said, maybe iPoker requires slightly more from your computer than other sites - but if your computer has enough RAM and you"re not running any memory intensive applications (graphics or video editing packages, etc.), then you should be OK.
Saying all that, watch me have problems with BlueSQ tonight...if I"m in the tournament long enough
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