Which version of Java are you using? Has this has just happened after updating LW?

Try updating Java (or reinstalling, if you already have the latest update): Java Downloads for All Operating Systems - Sun Microsystems

Download the offline installer & remove any other Java versions via Control Panel before installing this one. Restart your computer after installing the new Java.

You can disable AVG from within LW's options & then use your normal AV to scan files before opening them. In LW go tools > options > transfers. Untick the box to 'scan files I download for viruses' > ok.

Now you'll just have to scan all downloads with your normal AV before opening them - as you would've done in the past