Why is iMAC hanging up and Firefox crashing?

Question

iMAC is hanging up  and Firefox has been crashing every day for 2 weeks
Since 6/2/12, Firefox has been crashing most every day on my iMAC.  Using Firefox help, checked plug-ins and several needed update, so I started wwith Adobe Flash and began having worse problems.  First, it did not seem to download, then the system would "hang" (spinning rainbow) for VERY long time (over 1/2 hour or overnight).  After shutdown and unplug power for 10 minutes, tried to start up and now it takes over 30 minutes with lots of hang time. Finally followed firefox help suggestion to "revert to default".  Not much help and of course favorites bar is gone. Has still crashed at least once since 6/15/12.
Tried using Safari instead of Firefox and performance was HORRID-- very slow and lots of hangups lsting 10 minutes and more.
Via my iPad, I looked at Skype and history showed several entries for "URGENT ONLINE REPAIR" and others starting 6/2/12 (Same date as most recent string of Firefox crashes.  Possibly related??
Any ideas?

Answer 1

No smoking guns in the panic log that I can see. Does it KP in Safe Boot? Hold shift down at startup chime. Give it much longer than a regular bootup.
http://www.thexlab.com/faqs/kernelpanics.html
http://macs.about.com/od/usingyourmac/qt/Troubleshooting-Os-X-Kernel-Panics.htm
Faulty RAM is often a cause. Test the RAM with Memtest.
To test the memory, get memtest and run it in single user mode, where it will test as much memory as possible, more than with the OS loaded.
You can get memtest + directions from the link below. However, ignore running it from Terminal. Instead, boot into SU Mode, Cmd-s at the startup chime. (Best to startup from a full shutdown.)
At the prompt, simply type /usr/bin/memtest all 3 -L (From this link It will be installed in /usr/bin/) Then hit return. This will run three loops of memtest and create a log in Console in Utilties.
If you want to run memtest longer, which may be advisable, since RAM errors can be very elusive, just remove the "all 3" which will give you /usr/bin/memtest -L and hit return. It will keep testing until you quit it.
If you want to quit the test, just hit control-c
When finished, you can just type in "reboot" and hit return.
http://osxdaily.com/2011/05/03/memtest-mac-ram-test/
Direct link for the download.
http://cdn.command-tab.com/2008/memtest_422.zip