Image resize failed

[w0lly89]

Hi,

I'm trying to add an image to a post, or into a CMS article, using the "Insert Image" icon, then selecting an image from "My Computer". When I upload the image, I get the error,

"Image resize failed due to inability to obtain image size".

I've not had this problem before. The image I'm trying to upload is around 100k, and is 600px x 600 px, so it's not a huge file.

I've tried it on IE and Firefox with same results.
I've not upgraded my version of vBulletin recently.
Tried uploading as PNG, didnt work.
Dont want to use Imagemagick or GD, just want to use regular upload.
Tried every image size.

Please help

Thank you.