Just bought the script, and am very happy so far, good work 8)

One thing that is troubling me, is trying to upload a profile picture. It constantly gives the "Invalid file format. Only JPG extension are allowed". I have tried different photos, and tried altering them in photoshop, but with no luck.
Any ideas what might be wrong?
I don't suppose it needs to be a .JPG instead of .jpg ? I have tried this?