Version of phpBB2: 2? It's 3.0.4
Was this a fresh install or a(n) update/upgrade/conversion (please be specific)? upgrade from 2.0.21 using the provided upgrade tool.
Did you use an automated wizard provided by your host to install phpBB? No
MODs you have installed: None on new system. It was a test upgrade.
When the problem started: immediately
Your level of expertise (be honest): honestly

Additionally, you may wish to provide the following (where applicable)
Template(s) used: std.
Language(s) used: english.
Version of PHP used: PHP Version 5.2.4 Build Date Oct 11 2007 20:20:22
Database and version used: mysql
The last line of the index page says:
Statistics
Total posts 55698 • Total topics 2434 • Total members 1000 • Our newest member xxx (not relevant, but it is correct)
I get the same information from the ACP. I did synchronize statistics with the ACP. No change.
In fact, we had 1300 members according to SQLYOG, I deleted a bunch (it's a throw-away test board) and we're down to 1210, again according to SQLYOG, but the display still says 1000.
I tried searching for 1000 users in the support forum, but I got too many hits, because 1000 shows up all over the place, and so does users.