Whatever the range is in one hand, the range has to be the same for the other (so no close/thrown, close/extended combinations are allowed).And if *as you have seen) an item is cursed, once you use it, you can not switch back and forth between your primary and alternate weapon selections.
There is a remove curse scroll, though it may not be powerful enough to remove it either ... you might be *stuck* with it for a while 
Tools for Wizardry(r) 7
The power of the Bishop's un-curse ability is based on his/her level as a Bishop. A level 1 Bishop will NOT be able to un-curse the Cane of Corpus.
I don't have any personal experience with the Cane of Corpus, not yet anyway. Soon, very soon though.
In one of my earlier games, I got a Poison Dagger from Burz's chest. I didn't realize it was cursed and my level 2 Bishop couldn't remove it. At first I thought I was doing something wrong but someone on the boards said that this built-in ability was level dependent. I didn't try to remove it again until my Bishop was at level 6. She was successful but she probably could've removed it before then.
If your Bishop doesn't have the spell (I wouldn't waste a spell pick on it though) wait until the next level and try again.
Spence