Webserver which is hosting multiple sites on IIS 6.0 gets stuck after a few hours. Webserver Responds but DB does not

Question

IIS6.0 frame work 2.0

sql server 2005

My webserver which is hosting multiple sites on IIS 6.0 gets stuck after few hours..the response comes from the webserver but the DB is not responding..it again comes up only when we recycle the Application pool for the sites from IIS...we have latest configuration on the server and we cant restart the server as it will clear all our sessions....but whenever recycle the application pool from IIS it starts working again....