Random Program Closures

I recently upgraded the RAM on my mbp to 2gig, I bought this 1gig ram: http://www.crucial.com/uk/store/mpartspecs.aspx?mtbpoid=6DA0A421A5CA7304

I did the upgrade myself but I've done ram upgrades on a few laptops so I'm reasonably confident in my abilities, but ever since I upgraded firefox and finder has been quiting for no apparent reason and scrolling has been 'jittery' I'll scroll down and it'll jitter and get stuck and I'll have to start scrolling again.

Is there any mac software to do a memtest? (preferably an app if such a thing exists - I'm not very comfortable with mac boot ups etc as I'm still a mac n00b)

http://www.memtestosx.org/

Haven't tried it though - just found it through google. Looks pretty much straight forward.

I feel so stupid for not being able to find anything on google, I obv didn't look hard enough! I also have no way of paying :s

OOps.. I didn't try to download it to see, that you have to pay

So let's get to my second google result: http://guides.macrumors.com/Testing_RAM

That looks pretty promising. They have something about that "Remember" http://macupdate.com/info.php/id/15837 This one is free, I downloaded and started it. Will see what it says about my RAM