You need a SSD with cache. I had the same problem with every SSD I tried that didn't have cache. the 32GB SSD had the problem much more so then the 64GB, and the 128GB had the problem less then the 64GB, none of them had cache. When I found a SSD with 128MB of cache I stopped having this random freezing problem. I think the problem is the hard drive can't keep up between the virtual memory writing/reading going on, and other background task running.