The list isn't an exceptions list but a list of supported P2P applications.
avast isn't a firewall so it shouldn't have any impact on access for sharing, avast doesn't block only scans and if infection is found there will be an audible and visual alert.
Are you getting any error messages, if so what ?
Is avast alerting on the mp3rocket executable ?
I'm thinking a possible issue with remnants of Norton.
A link worth looking at, which is a program removal tool that can remove the remnants of a number of different Norton Programs:
Removing your Norton program using SymNRTYou can also download
SymNRT, a Norton uninstall tool that uninstalls all Norton 2004/2005/2006 products.