Your php.ini has a max_execution_time setting which is by default 30 seconds. If your uploading many pictures at a time I can definately see it timing out. You would need to edit the php.ini and up this setting and restart your server.
You can see if this little snippet of code will help if you do not have access to edit the php.ini
When you say "my host" do you mean "my ISP" or, as the administrator of my site is this something that I would find somewhere? I could not locate this file on my website.