ruby 1.6.8pre + Tk = 100% CPU?

< ^ > P N |<>|^_>< --- | ~ ...Help

I'm using the 1.6.8pre.  I notice that the ext/tk/sample/tkhello.rb uses
100% of the CPU.  This was not the case with 1.6.7.  I take it this is a
bug?

%ruby --version
ruby 1.6.8 (2002-11-09) [i686-linux]

Tk version 8.3.3