I'm working on a project which includes a number of light bulbs with the Stylize Glow effect added to them, animating the intensity and radius to increase. The animation is running perfectly in the RAM previews, however, when I render a default lossless video file, the glow is gone and replaced with a transparent ripple effect. I was wondering if anyone had come across the same thing or more importantly if anyone knows a way of solving the problem? I am working in After Effects CS6
No clue -- we don't know anything about your machine, your OS, and your PRECISE version of AE. They make a difference.
Nobody can tell you anything without proper project info or other technical details like exact render settings, bit depth, effect settings and so on. From color range issues when converting to 8bit CoDecs to transparency threshold issues in the glow source this could be anything.
In addition to the info others have asked for, could you show an image or video to demonstrate the issue you're experiencing?