[plt-scheme] DrScheme startup error (Windows)

Hi there, I just kicked off DrScheme (4.2/Win32) today and have been
greeted with the following error:

draw-bitmap in dc<%>: expected argument of type <bitmap% object>;
given #f

 === context ===
C:\Program Files\PLT\collects\drscheme\private\drscheme-normal.ss:
208:15

I've had a hunt around and could find no information on this, and I've
reinstalled just in case a bitmap or some such file was corrupted, but
no luck.

Any ideas? Much appreciated,
Simon.