We are having the same problem using glassfish V3.
1 to 3 times a day the server is simply just not responding to any request for 1 or 2 min.
That apply to static content and web services.
I was thinking this could be related to the jvm garbage collection, I am currently in the process of tunning this.
We are on Centos 32 bits, java 1.6u16, glassfish v3b10.
Vincent