Hmm, then it seems to me that would point to some kind of web server configuration issue, although I'm not sure. Hopefully someone else will know more.

Check your config.php file and make sure you didn't save it as UTF-8 (with BOM). It needs to be edited with a plain text editor like notepad++ and it needs to be saved without the BOM!

Lynne, thank you for replying.

I always edit my files using FileZilla as my FTP client, which allows me to edit the files using notepad.

--------------- Added [DATE]1391023948[/DATE] at [TIME]1391023948[/TIME] ---------------

Thank you for your help, I really appreciate it!

I'm pretty sure Lynne is right though. I looked and you actually have those 3 bytes (a BOM) at the start of your forum pages, but it doesn't affect the html. But it's almost certainly because they're at the beginning of your config.php file. If you don't have a programming editor then get notepad++, edit a new copy of config.php on your PC, then upload it via ftp.

I've edited an original copy of config.php on my PC and uploaded it via FTP. Unfortunately, no change.

Did you use something other than notepad? It could be that the problem is somewhere else, but I'm just making sure. It's actually one of those problems that comes up fairly regularly, but usually it's someone getting an error message that says "headers already sent".

Another thing I suppose you could do to verify that it's not a web server issue is to take one of the files, copy it under public_html somewhere, then download it directly and see if it comes through OK.

You have a lot of odd characters on your site which would lead me to think the database wasn't transferred correctly. Did you import it using the command line? Did you make sure when you moved it to the new server, that the new server mysql was using the same collation and charset before you imported it?

I edited with notepad++ as suggested.

I can download files fine when I upload them to public_html

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This is what I am thinking. I requested that my host transfer my website files/database over to the server, which they did.

I am considering uploading a back up database from last night and I've also got back up files from a few days ago which I am also considering overwriting the current files.

Do you think this would make any difference?

OK, then it seems like a problem with vbulletin. Lynne's the expert, but I'm not sure how database problems would affect the attachment downloads, so I'm leaning toward the vbulletin files. If you haven't modified the files then it couldn't hurt to upload a new set, as long as you can get the owner and permissions right.

Restored everything to the 26th, files/database the lot and the problem still hasn't changed.

That seems like the last resort and I've run out of ideas now...