I've now asked the server people (hostgator) if they would look into it for me, which they kindly did.
I gave them access to my ACP so they could see the problem for themselves, and they did. Sometimes you can add games and sometimes you can't, and it's becoming a case of can't more and more often.
The server people seem to think it's happening because there's a huge amount of files in there and the system just can't cope with loading it all up so it eventually fails.
Does anyone know if there's a solution to this, can i delete any of the tar files without losing the games? Or is it just a case of not loading up any more games? Or would a different host be the solution?
BTW, I have about 7500 games installed in my arcade so I don't think there can be many more to get but it's just a pain not being able to access that part of the ACP.
Thanks guys & girls