Mini started freezing!

Hi, I bought an external blu ray drive for my mini a few days ago. I tested it out and copied 1 of my films to the hdd using makemkv.

I tried watching the film last night to see if it copied ok, and about half way through the film, my mini completely froze!. (had to hold the power button on the back until it turned off).

Then when my mini was up and running again, I thought maybe it was because of the film being in mkv, so I tried converting it using handbrake. Well after around 20% converted, my mini froze again...

Today I left my mini for awhile while I ate my dinner, came back, and it was still working fine, but when I moved my mouse to stop the screensaver, my mini yet again froze!

I know watching large mkv files gives the cpu a workout, and it was running at around 90c. But my mini when using the screensaver usually runs around 55-60c. So I guess that rules out overheating?

I wondered if it was my RAM, so I tried out memtest, I only ran it through all the tests once, because istat was saying my cpu and RAM were at 72c and the fans were going crazy!, but the RAM passed all the tests.

When I start up my mini after it freezing, it doesn't say anything about a kernel panic or anything. So I'm out of ideas.

Anyway, heres my mini's info:

Processor: 2.7 GHz Intel Core i7
Memory: 8 GB 1333 MHz DDR3
Software: Mac OS X Lion 10.7.2 (11C74)
Graphics: AMD Radeon HD 6630M 256 MB

The hdd is just the basic very slow 500gb hdd that the mid minis come with.

I decided to try removing any software I had installed in the last couple of days. (handbrake, and 2 screensavers), to see if that was the cause, before resorting to changing the RAM.

I ran memtest again, and the RAM passed all the tests again, and so far I haven't had any freezing. *touches wood*

I know it froze once when converting a film with handbrake, but can it freeze the mini while not using handbrake?. Like from just having it installed? (maybe it runs in the background or something, even when I'm not converting videos?).

Also has anyone heard of installed screensavers causing freezes?. It froze once when the screensaver was on and I moved the mouse. (was using a screensaver called lotsawater).

Another thing I was wondering is if the new blu ray drive could cause freezing... It is powered by the mains, so I assume it shouldn't be trying to draw a lot of power from the usb, which could cause freezing?. The blu ray drive has been plugged in all day though, and theres been no freezing yet, so I'm guessing that wasn't the problem. (this is the blu ray drive I'v got: http://www.dabs.com/products/lg-ele...ata---usb-2-0-7VPS.html?refs=4294953226&src=3)

Next plan of action if it freezes again is to try removing the blu ray drive. If that doesn't help, then I'll try swapping the RAM. I put the RAM in the day after I got my mini, and it's been working fine. So I'm guessing it's something thats changed recently thats causing the freezes.

Bah, soo confusing lol. On my old PCs, freezing was usually to do with the graphics card, like the drivers for it. But I'm all up to date on my mini, and tried playing Flatout 2, and had no problems.

Just an update. Since uninstalling handbrake and the 2 screensavers, I haven't had 1 freeze!.

I also ripped another blu ray last night (using MakeMKV), and watched it (using MplayerX), no problem at all.