group by bug in 6.2.1 & 6.3 -snapshot

Hi

I find next bug:
in query "select a,b,count(*) from q group by a,b;" postgres do:
a ,b ,count(*)
5 2 3 ???
5 2 2 ???
6 3 6
.................

table - about 10000-30000 tuples.

PS: i use linux 2.0.33 & solaris 2.5.1

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SY, Serj