It happened when they all had the original names too though .. that was just my latest attempt at loading that I uploaded
Make sure you used the correct name for the zip "zBCIC2crossover server v1.18.zip" note the z.
If that doesn't work, then make all the names the original. (Backup the save) Then try running the server with just IC2 and BC. if that works then add my mod and see what it does.
An explanation, the class it is looking for is in the buildcraft core zip. It just has to load that first. Also what OS are you using?