Images Dissapearing After Upload

Hi people

I am currently working on someones blog and i recently upgraded to the latest version of wordpress.

The problem i have is that i am uploading an image using wordpress inserting it into the blog and all is ok. Then when i check back the image has gone, The image holder is still in the blog post, the image entry is still in the media library but it has gone from the uploads folder. (on the server)

Using FTP’s i have confirmed that the file is being uploaded, the image URL displays the image when it is first uploaded yet it dissapears. Originally noth the filenames had underscores in them and for one of the images removing this seemed to have solved it.

The images are of a small file size (4k) and in full colour. they are jpegs.

I am the only person currently working on the site who would be using the server so i have ruled out the idea of someone deleting them.

I have searched and read the forums to try and find help but nothing quite matches my problem.