whats the min. connection pool parameter in JDBC connection setting ?
are your IS and database located in same LAN ?
We faced similar issue with IS 6.5 which was located in one country and database was located in another country.
I think the cause was aggressive polling set.(20 sec). Because IS took itself took time connecting to database which was in another country and then was not able to poll. The first polling was not completed before next polling starts.
Do see any error message in server log ?
#Integration-Server-and-ESB#Adapters-and-E-Standards#webMethods