We need a lot more information that what you have offered in order to suggest where to begin.
Generally speaking, it is not the kernel causing a freeze The most likely culprit is the video driver.
By freeze... do you mean screen locks, mouse pointer does not move, keyboard does not work?
Can you Ctl+Alt+F1 to a terminal, log in and type dmesg? Look at the last few lines for a hint.
Is the 'freeze' consistent with any application? What application are you using?
Do you have ATI video? Did you upgrade to ATI driver in sid?
Do you have correct driver for your video card? If it is ATI, someone else will have to help further. We have no ATI in our house.
The 2.6.38 kernel is a good one. I use it on all of my machines except for the old desktop which is our entertainment center player.