Queries very slow and memory consumption too high

Hi,

I am using Postgres 8.2.10 + Hibernate + c3p0 connection pooling.
For our application we support MySQL + Oracle + MSSQL + Postgres.

With all the other databases our application is working quite fine, but with Postgres after a day queries are becoming extremely slow and it seems to be taking up all the available memory.

Please let me know what could be the issue. I am new to Postgres, so any help would be greatly appreciated.

Thanks,
Saurabh