Comment 190 for bug 50214

Dima, maby you should have look on Bug #208306 "[ath_pci] cannot connect to hidden ap", which deal with the Atheros based adapters. Using the patch attached do make my 3 different Atheros adapters work.

I've testet Kubuntu from Edgy to Gutsy on a ThinkPad T21 several times, and my experience is that thees laptops (T20-23) is getting rather old for thees new OSs. It seemed to me that the amount of RAM and the Prossesor speed (700~900 Mhz) has a certain influencer on NetworkManager. Mine NM did crash too with Gutsy, using PCMCIA with both Atheros AR5212 and other chipsets. Installing more RAM (128 -> 256 -> 512 Mb) did change things a little as fare as I remember.

Did you shutdown/switch off the buildin ipw2915abg in BIOS on the T43 while you tested the Atheros ?.
Having both Adapters activated on the same time, seems to help the Atheros finding and connecting to a specific hidden SSID - when the one adaptor (ipw2915abg) have made an initial connection first.