I am attempting to upload a new custom header image, but receive an error upon each upload. i'm taken to http://wp-admin/themes.php?page=custom-header&step=2 and the error in FF is: Server not found, Firefox can't find the server at wp-admin.
My image is an average filesize .jpg (about 30kb)
I'm using Firefox v126.96.36.199 on XP Pro SP2.
incidentally, i get a smiliar "page not found" when uploading an avatar, although i DO get to the cropping stage with this - the problem lies on http://wp-admin/avatar-upload.php?step=2 for me.
Any help much appreciated - just purchased custom CSS and itching to progress!