funny behavior isn hash tables?

["Roland Zito-Wolf" <rjz@chaos.cs.brandeis.edu>]

I just ran into a bit of odd behavior w/hash tables.
They'd never given me any trouble till I added  a 
function to collect some statistics about the contents of
the tables. It MAPHASHes over two tables and throws out
when it finds what it wants.

The peculiar behavior is: the data in one of the tables
gets destroyed by doing this, sometimes. I examined the
tables; the broken one had the right value (131) in its ENTRIES
variable but only 43 actual entries, all of then in
bucket 0. The undamaged table had entires in all bucckets
but 0 and one other. I shoudl add that this happened 
while the program is GCing reasonably often (every few minutes).

Any ideas? 
-roy