JPEG weirdness - not showing up for Windows users

Okay, here’s a real head-scratcher.

I’m a Mac user, running a Mac Pro, Leopard, CS3.

In the last month or so, the Windows users in my company cannot see images in JPEG files I send. The file opens, but the image is blank. PDFs from Photoshop work fine.

I AM STUMPED. I have no idea why this should be happening.

A friend reported that if he “Saves As…”, renaming the file plus manually typing the file extension (.jpg) it then functions normally. But he’s a bit more savvy than most in the company, and besides, nobody should have to go through such steps.

Any ideas?

thanks