Macbook model A1342 randomly freezing I have a Macbook white model A1342 that I'm fixing for a friend of mine.

The macbook will freeze up totally randomly (usually while surfing the net but it happened even when no browser was opened). Freezes are usually 2-3 per day, but once it starts freezing it will freeze again in due time
It freezes without any beach ball spinning up, the cursor remains where it is and the only solution is shutting it down via the power button.
When I took it from my friend for fixing, it had only 2gb of ram and mavericks installed, and was painfully slow. I thought that was the culprit and installed 4gb of RAM, but it freezed again, today, just after installing the RAM, like nothing changed.
AHT and memtest won't report any errors, and the system log reports warning like disk swapping but nothing too dramatic. Tried etrecheck too, apple support's app for checking your system and nothing wrong reported here too.
Here is a list of what I tried so far:


upgraded to 4gb of RAM
clean reinstall of mac os lion
tried swapping disk, Mac freezes the same.
opened up the bottom lid and checked if fan is on, it seems to be
working ok.


I should add that the macbook has an erratic airport card. It often won't get detected by the system. Could a faulty airport card be the culprit of these freezes?

I'm pasting what the system.log reported just before this morning's crash (I don't know if it helps):

Apr 29 12:30:44 macbook-di-luca iBackup[376]: "download and install new plugins"
Apr 29 12:30:54 macbook-di-luca mdworker[327]: (Error) Import: Couldn't recover plist from xattr com.apple.metadata:kMDLabel_xjx7qauyg5mltgjdmyyeartz4e     
Apr 29 12:31:41: --- last message repeated 5 times ---  
Apr 29 12:33:16 macbook-di-luca KernelEventAgent[43]: tid 00000000 received event(s) VQ_LOWDISK, VQ_VERYLOWDISK (516)   
Apr 29 12:33:17 macbook-di-luca Finder[125]: _GetISImageRefFromIconRefInternal: could not retain image ref 0x213c0055 (err=-2580)
Apr 29 12:33:17: --- last message repeated 1 time ---   
Apr 29 12:33:17 macbook-di-luca UserEventAgent[11]: Cleaning up local snapshots on volume file://localhost/Volumes/WD-GIGI/ 
Apr 29 12:33:20 macbook-di-luca Finder[125]: ISGetIconFamilyFromStorage: seed mismatch for 22c20010, actual seed is 109cf92e    
Apr 29 12:33:20 macbook-di-luca Finder[125]: ISGetIconFamilyFromStorage: seed mismatch for 213c0055, actual seed is 39386575    
Apr 29 12:33:22: --- last message repeated 1 time ---
Apr 29 12:33:22 macbook-di-luca xpchelper[481]: for uid: 501 -- timeout while waiting on FSEvents flush; clearing cache.


After that it freezed up for good like usual, without any warning. 
Thanks a lot for any suggestion and help in advance. I'm quite discouraged and can't seem to find the solution to the problem, and I don't want to start swapping parts randomly.
new SSD and new RAM didn't help similar problem here. Also missing airport on reboots occasionally. Suspect it's a current leak problem on the system board. No easy solution to that. Good thing is the fast reboot with the SSD.