I've been going through the tomb to find the Lich, and I've gotten to the room that has Phreya and the unnamed Lich. The Lich will not die and Hexxat keeps repeating the same speech over and over again about us having killed the wrong LIch. I don't know what to do and I seem stuck at this point. Can anybody help me get through this. I don't want to lose Hexxat, but I fear dropping her may be the only way I will get past this glitch. Any suggestions are welcome. Thanks.

Nevermind. I got it to work with some help from the Beamdog forums. Apparently, its a glitch, so you have to cast "Imprisonment" on the generic Lich and also make sure Hexxat has her cloak when the dialogue pops up. I was able to finish Hexxat's quest that way.