Screen Freezes but cursor still moves

I have a reoccurring issue with my macbook air, it freezes but the curser still moves. I was originally told it was a hard fault so i migrated my mac onto another macbook air, but i still have the issue. I have been trying to look at the system logs to see if anything stands out but I can see anything. it last froze 30/09/2015 @ 15:21. I have found sometimes if i leave the machine for 5 minutes it will fix it's self, but 90% of the time I restart it. I need a fix quickly before my manager makes me get a windows machine😟.

Any advice would be helpfully.

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