I should mention - I love McAfee NSP. I think it's a great platform that does a good job. I really enjoy using this product. The Java thing is really frustrating though. Once that is gone, this product will be amazing.
It is strange.
I use Win7 32bit with Java 7 SE Runtime Environment (build 1.7.0_45-b18) and Firefox 26 with NSM 220.127.116.11. Have no issues.
Do you have 32bit OS or 64bit ?
What NSM version are you using?
Does the RTTA work every time if you use it directly on the NSM server?
The issue seems really random - some days it works fine, some days not. I contacted support yesterday because I couldn't get it to work at all and they advised upgrading to 18.104.22.168 which I did. It has opened the couple of times I have tried it since then, so I'm hoping that sticks (though I'm not counting on it too much, I've had this issue off and on since the v6 days). I will just be so happy when Java is gone! This could all become moot though once we get Nitro- that interface is awesome!!!