Okay you know the way down to lower dornes deep. After the whole Jorial and the frost giant escapade. When I try to take that cave down in the southeast the game crashes on me. It says something like. An assertion failed in infinity cpp at line number 1763. Programmer says: Demand for WED file failed.

I have a patch installed and any help would be good.

Back up your saved games first and then try uninstalling, defragging your hard drive, and reinstalling using a FULL install if you haven't done that already.

Make sure you have the proper patches installed. For IWD only, use the v1.06 patch. If you have HOW installed, use the v1.41 patch. If you have TOL installed do NOT apply any additional patches.

Happened to me in BG1. Uninstall/reinstall didn't work. It turned out my cd-rom drive was corrupt some how, but I didn't realized that until my computer was formated :(
Well, hopefully, that is not so in your case.

A demand for a WED file implies that either (A) your computer is unable to access a file off the cd-rom, or (b) it can't access a file installed from the cd to the HD. Reinstalling with a FULL install may clear up a file that was garbled during installation, and minimize the likelihood the getting that error from accessing the cd-rom.

It IS possible however that your cd is simply bad or your cd is failing. Check the cd out for obvious scratches and clean it. There have been a number of posts like yours on the BIS forums. Some have been solved with a simple reinstallation, others have been the result of a BAD cd.

Assertion Error at line 1763

I had this error the first time I played the game, as you say it prevents entry to Lower Dorns Deep. I then checked the Interplay web site which listed it as a known bug, so I downloaded the fix and everything was ok after that. So, Jabidas are you sure you have the correct patches, it may be that this only happens in the UK version. Let us know if you have fixed the problem, so we will remember if it happens to someone else.