In case you missed it, there was a post on our forum here:

http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1366051&SiteID=1

and a comment on my blog here:

http://blogs.msdn.com/davbr/archive/2007/03/06/creating-an-il-rewriting-profiler.aspx#1881536

about an issue with GetILFunctionBody returning the wrong size.  This is indeed a bug in CLR 2.x, and it is recommended you follow the ECMA spec help you parse the function header to determine the actual size.  More details are in the forum post linked above.  This bug will be fixed in a future release of the CLR.