Minimum computer specs for GR and/or mini-applet?

I have a gallery install that I am providing for family members to upload and store photos. A number of them have older computers, still running Windows 98. I've installed Gallery Remote (with VM) on their machines but have run into a bit of a snag.

Screens within the local install of GR and even when using the mini-applet or larger applet from the online upload form do not refresh properly.

By this I mean, if you do something in the application that requires the screen to re-draw, it doesn't actually refresh and show you what changed unless you click somewhere on the application a second time. It would appear that this happens only on older and slower machines. Why would this be?

Hopefully this post makes a little sense. If anyone has any experience running any of the Java Applets on older hardware, let me know if you had to do anything to get it to actually work.

Thanks.