wrong results from "Select count(*) from tbl"

I am the user of an Oracle DB and I am getting what look like wrong counts using "Select count(*)" statments.

It first occurred when I tried to get monthly record counts with   Select count(*), month
  from tbl
  group by month
All the monthly counts but one looked like it was 2x what it should be.

Oddly enough if I tried
  Select count(*), month
  from tbl
  where month = 200302
  group by month
OR
  Select count(*), month
  from tbl
  where month in (200301 200302)
  group by month
I got what looked correct.

I even got the 2X problem when I asked for a count on the entire table using
  Select count(*)
  from tbl

One of our DBAs suggested the problem has somehting to do with the indexes and not running analyze on the table recently. I'll note also that the table is partitioned.

I think it's Oracle version 8.x running on a Sun box.

Has anyone seen this before or does anyone have any suggestions on the cause of the problem.

Thanks,

• john