Im having similar issues, on and off.
Recently, Ive been messing around with new roms and and kernels and found out tinkering here and there that when the tablet is put to sleep, its supposed to go into deep sleep, this being what makes the tab super battery efficient when its sleeping
A quick test to see if its going to deep sleep is to download Cpu Spy free from the market, start it, go to options (top right) reset timers to get a fresh reading, put tab to sleep for 10 -20 secs, then turn on, go back to Cpu Spy, options Refresh. You should have a listing for deep sleep, which will tell you that deep sleep is at least working.
Every now and again i would test this, found out that sometimes deep sleep would not initiate, normally its ok straight after reboot, but after ive been using the tab (mind you, not always), and test deep sleep, i find that the tab would stay on a low clock speed rather then deep sleep, well 'low' being a relative term, i mean at some points, the tab wouldnt go below 475mhz even when idle.
When idle, ideally, the tabs if not doing anything intensive in the background, SHOULD go to the lowest CPU state, 102mhz, i think there is something, either system related or app related, thats forcing our primes to run at higher clock speeds and in some cases its not letting our primes go into deep sleep
I think using cpu spy, is a good tool to figure out what that might be, restart your tab, before doing anything, establish that your tab can go to deep sleep while sleeping and uses the lower cpu speeds when idle, and then test it everynow and again, if the issues come back, and you see a connection between a certain app or certain setting you've been using let someone know, chances are, it could be our culprit, in this case the best way to fix something is to find out what needs fixing.