Chromium vs. Firefox (off topic)

[Gerry]

I've been following the thread about the relative merits of these two, for me this is academic; since upgrading to 13.04 all Mozilla products hang my machine e.g. Firefox, Thunderbird, Seamonkey. I've tried purging the packages & reloading, I've tested the memory with GRUB, I've changed the NVIDIA driver to a proprietary. The problem is intermittent but once is too often. If I fall back to 12.10 the problem does not manifest itself, what has changed? Is the problem in the Linux Kernel? Maybe one of you good folks has some advice. 
The good news is that I'm using Midori & liking it :-)) 
(AMD sempron 2800+ 64 bits 1.6 GHz, 875 MB RAM) 

-- 
Gerry <gerry.gazules>