Cannot create thumbnails

[RexTheRunt]

Hi
I've tried finding a solution on the forum - sorry I can't!
I am able to create thumbnails after uploading .jpg images, but I cannot from .png or .gif images. The images appear fine in my media manager.
I get this message:

Error Message: Error while Creating Thumbnails (ThumbnailExists)
What to do now : » If you have fixed the problem caused by

* Image (wrong type or broken image) - remove the image or upload new image via e.g. FTP
* GD Library (not correctly working GD library, not working GD functions) - install or reinstall GD library
* Permissions (no rights to write files or folders) - change the permissions of image/phocagallery folders on your server,

I don't have any duplicates and I don't have ownership/permissions problems - the jpg images are fine in the same folder.

Can anyone advise me?

Thanks!

[Jan]

Hi, this error message is comming if there is existing thumbnails but such cannot be overwritten by new thumbnail

[RexTheRunt]

Thanks for your reply Jan.
There are no existing thumbnails! I have tried several new folders and files and the only ones that work are jpgs. I can even overwrite the thumbnails that were created with the jpg images if I recreate.
Any ideas?
Thanks.

[Jan]

Hmm, then there must be some problem in GD (png, gif) or the png or gif are not correct and cannot be managed by GD