Yeah, I have had that problem. I wish UAE was just a little bit clearer on what is not possible. For example, how much RAM do you need to stick your peecee with to use the leftover? I have 768MB RAM on my system, but I can only seem to utilize 8-32-32 (chip-z3fast-rtg).
Really, I think the problem amounts to incompatibility. I haven't had any problem after setting everything for hi-compatibility.
For example, I had no problems using Dave Haynie's DiskSalv4 -- but only after selecting the Quickstart A1200 4 meg configuration. I'm not too annoyed.
I couldn't get Colonization or Theme Park to play until I recovered an old 129 mb hard drive formatted for my A1200. I was amazed to be playing Colonization just a few days ago straight from my old hard drive (after I just changed its board I opened up access to data I thought I would never have enough money to afford, plus I got my 3.x Miami keyfile restored to me--and that means a lot, Amiga-wise!!)
I'm just annoyed that I can't use Miami on UAE!! And then, I have Genesis with OS3.9.
But yeah, UAE would just ignore you if you want to use any PC Hardware that isn't explicitly tweaked by Cloanto for 100% compatibility, but the vast majority of my problems with UAE I think have answers and can be addressed. Within Cloanto's definition of compatibility, I think we have 100%; but it's not the Amiga until it has her hardware base to choose from, and that's not going to be an internal PC modem or a PC-format hard drive, although Cloanto has evidently given users the ability to make use of hard drive functionality in-a-pinch.
MY big annoyance with UAE were that I can't seem to boot into my usual configuration AND read an Amiga-formatted drive at the same time. Not yet, anyway...
Aniway