This happens all the time with windows and java, it matters not what browser you use. AV will show legit java files as a virus just as AVG shows legit .bat files from Mastersplitter as viruses.
I encountered this a few months ago and deleted the files that were causing the problem and ended up with even more probs as I could not access many websites including the sun java site it'self! Fortunately I had saved the jre install file and was able to sort things out after completely deleting sun java from the registry and programs. and then re-installing.
It is one of the anomolies of AV progs that certain types of file will be seen as viruses but are actually required. Sun Java is a well respected company and software. I have had no problems since and all security progs report no suspicious activity from them. They still show as viruses but do not cause me any headaches.
Hope this helps.