I built a newer version of TiEMU a few months back, which seems to work well except for being a bit slow. You can download it
here. I can't remember if I fixed the skin problem I was having in the .ipk, if you get an error about ipaq_ti92.skn, it's because the file is mistakenly named ipaqti92.skn and needs renamed to fix it (it could be the other way around; I don't remember exactly).
If you don't want to go through all that- the problem you may be having is that the original TI92 skin file is larger than the 640x480 screen, and it sounds like it's getting mad about that. If you can find the ipaq version of the skin file, it should work better as it has been reduced in size to fit a PDA's screen.