Are you using Necrosis 2.0.3b or Necrosis LDC?
If you are using 2.0.3b you can download the patched files from
http://cc.usu.edu/~rleikis/necrosisfix.zip
These are files I have patched myself and I guarantee them to work, they are virus free, yada-yada-yada... 2.0.3b is not exactly being supported any longer because the creator has little time to work on it and any new versions.
If you are using LDC, there is an updated release out which is easy to find, however last I heard it is still having numerous problems.
And yes, Necrosis has pretty much become a must have for any serious Warlock.