Sorry to bump an old post, but I confirm; deleting the cache fixes the problem. I didn’t have an %APPDATA%\LocalLow\cache folder. I went to %APPDATA%\LocalLow\Unity. In there, I found The folders “Browser,” “Caches,” and “WebPlayer.” All 3 of them have caches to delete inside of them. My cache was over 10GBs and I fixed my error by deleting it.
Anyone who comes in here from Google can have a fix that took me a long time to find.
For me, I realized Windows disabled paging files (virtual memory) so it made sense that Unity kept running out of memory. I just had to re-enable paging files. The exact process varies between the different versions of Windows, but for my Windows 8.1, here’s a screenshot: