uploading file error

I am using WordPress version 1.5.2 and for some reason I just started to get errors when uploading files. When I choose the file.jpg to upload I get this error after clicking upload:

Warning: imagejpeg(): Unable to access /home/harris/public_html/pictures/thumb-firstgoose.jpg in /home/harris/public_html/wp-admin/admin-functions.php on line 258

Warning: imagejpeg(): Invalid filename ‘/home/harris/public_html/pictures/thumb-firstgoose.jpg’ in /home/harris/public_html/wp-admin/admin-functions.php on line 258
Thumbnail path invalid
File uploaded!

Your file firstgoose.jpg was uploaded successfully!

Here’s the code to display it:

<img src=’/pictures/firstgoose.jpg’ alt=’gus with goose’ />

Image Details:
Name:firstgoose.jpg
Size:374.44 KB
Type:image/jpeg

As you can see it uploads the file but fails to create the thumbnail. I even ran chmod 777 on my /pictures directory. Like I said, it just started doing this so I have no clue. Line 258 says this:

if(!imagejpeg($thumbnail, $thumbpath)) {

Please Help!

Thanks