For what it is worth I never had the emu lock up on me (except for the games that don't work like Actraiser). I always play with sound on, and I am running FW 2.0. The only bug I have had is the sound loudness seems to shift back and forth between left and right speakers randomly.
Just found something on my gp2x...
Please do the following:
Start playing an MP3.
While playing, hold put your finger on the case onto one speaker. Then try the same with the other speaker.
Usually, if you cover the left speaker, you should hear the sound coming from the right and vice-versa.
Is this the case here? It wasn't.
When I covered one speaker, sound came from the other one, alright.
But when I covered the other one, the sound seemed to come from the middle of the gp2x - and sounded much better.
This happens if the phase for one speaker is wrong (which it was in my case).
I had to open up the gp2x and switch the red and black cable of one speaker.
After that, everything sounded nice and MUCH better - sure, the phase is corrected now...
Might be the problem on more than one gp2x (if not on all...)