Eric,
I came across this bug by accident. Its not important to me in any way but I thought you should know about at. It seems that any attempt to apply ##symbol-hash to a symbol composed of numbers, ie (##symbol-hash '33) of (##symbol-hash '5321) causes gsi to segfault. This may or may not have wider implications.
Well, '33 and '5321 are not even symbols. They are numbers. I guess that ##symbol-hash does not even check the type of its argument (like most functions whose name start with ##). So I wouldn't consider this a bug.
The following works, however:
Gambit Version 4.0 beta 10
(symbol? '|33|)
#t