I get the same exact error. This is the exact text as it reads in the map compiler:

Warning W072: block 0 - plane 31 too narrow!

Building fat hull ......ok
Building narrow hull......ok
Building BSP tree...

....CRITICAL ERROR.....

E701

Press any key.....

Really would like to know what I did here....
I have a city environment due in 2 weeks I am freaking out.

Shady