Hi David,
I had COM-problems with 1.6.1 which disappeared in 1.6.2.
Therefore I suggest to first upgarde to 1.6.2:
1) get
http://jarh.hoops.livedoor.com/ruby/ruby-1.6.2-20001218-i386-cygwin.tar.gz
2) unzip/untar it
3) copy the /usr/local/ruby subdirectory over the 1.6.1 installation.

Clemens