The spell check .sql file is massive. Basically a default PHP installation sets the script timeout to around 30 seconds. You need to actually modify the php.ini file which on shared hosting you cant do. to increase this. This is the case for both phpMyAdmin (as its written in PHP) and writeing a PHP script to do the job.
I would suggest a TikiFriendlyHost, however I have no idea that they have increased the timeout script value. I know it inserts and runs fine on my hosting http://tikihost.net maybe others can provide additional information on other hosts.
This is not a TikiWiki problem, its down to the hosting providing.