This site might be well known by some, but Canon has issued some service notices on the EOS 20D digital SLR. The most recent one is:
April 27, 2005: We have confirmed that the BG-E2 battery grip for the EOS 20D digital SLR camera causes issues such as the number of shots being limited or a low-battery warning being displayed immediately when used with a fully charged battery pack or a fresh set of AA batteries. Canon offers its sincerest apologies to all customers who have been inconvenienced by this issue.