I have a similar problem.
I changed my provider, so I got a new sim card.
The sim card work fine on a htc tattoo (older phone) but no on my acer liquid metal.
The phone was blocked on SFR network (but now I believe it's unlocked with the latest update), but that not the problem since my sim card is SFR too! (french network).
I tried another SFR sim, and same problem, it don't work on the acer liquid metal.
I tried two custom rom, lewa os (september version witch was working perfectly with my old sim) and the latest lewa os (february version) and I got a "no service" when I power the phone, and I don't get prompted to enter the sim code...
I tried another custom rom (holo-cm7) but same problem.
So I decided to flash the stock rom, and with the stock rom it work!
But I want a custom rom, so I tried to flash again a custom rom with full wipe, it doesn't work.
Then I flashed a custom without any wipe, with the hope that my sim card will be seen, but no luck again.
I tried that with the 3 custom rom I mentionned above (so it took my all the afternoon for nothing xD).
After I tried *#*#4636#*#* and changed all the network settings that I can (cdma, gsm, gsm prl, gsm cdma prl auto, and I don't remember the others lol).
But I never get promped to enter the sim code.
I'm really desespered, so I hope someone will know what this problem is related to, because now I became crazy!
Thanks for the help, and sorry for this long message, but I wanted to explain all the problem.