Performance Problem

Hello,

we have a performance problem with PostgreSQL 7.2.4. But first I try to
explain our situation:

We have an online game. This game is a fantasy game, where you can buy
and sell players for your team.
All players for the teams are stored in one table. So in this table we
have just one primary key and to foreign keys.
When we have around 500 Users at one time on the maschine, the game is
slowing down(Time for one spage up to 1minute and more).  And I think
the problem is this table. There are a lot of reading and writing
connections to this table.

So now my question: What can I do to increase the performance?

Thanks and greetings,

Stefan Sturmn