Big Applet Upload Error when integrated with Mambo

I'm using Gallery 1.5 and Mambo 4.5.2.3 and the integration is working very well - except when I try and upload images. I quickly determined that I need to enter the site with www in front of my domain name for the "add photos" popup to work...but that's not a problem.

If I use the Big Applet (aka Gallery Remote) to upload images within Mambo, I routinely get an error if the image has a large filesize. The error is:Upload error: Upload failed: 'Invalid image: xxx.jpg'.I am able to successfully upload the image with the big applet (Gallery Remote) if I use the stand-alone gallery URL. When I use the same process within Mambo even using the same image I get this error. I've searched the forums for answers and am unable to find any info about this unique problem. Any help would be much appreciated.