1) Update Iceweasel the current version is 14.0.1 use the mozilla.debian.net repo or backports for the ESR version
2) update flash
3) update Java
4) start Iceweasel in safemode if it doesn't crash the problem is most likely an extension or theme
5) Create a new Iceweasel profile
6) move .mozilla to .mozilla.bak
7) install iceweasel-dbg for more detailed crash info
Troubleshoot and diagnose Firefox problems | Troubleshooting | Firefox Help :
https://support.mozilla.org/en-US/kb...refox-problems