I had some weird Java issues when I went to 7.5 2 weeks ago or so with the console. I started up CMS in private browsing session, worked fine. Went back to normal browsing IE session and it continued to work.
I upgraded to java 51 yesterday and haven't had any issues.
Maybe the private browsing trick will work for you... also make sure there isn't a java prompt waiting for your attention in the background/hidden. I saw this today with a software import (I run on medium as well).