a_berezin:
To know how to fix need to know what the problem is. Check server error logs.
... if you have access to these logs
a_berezin:
If the problem is in the limit on memory, try this.
- Increase the memory limit.
- Go to Admin -> Configuration -> Sitemap XML -> Check Dublicates set to false or mysql.
If the problem is in the execution time limit try to use cli interface for cron job.
Andrew's suggestion is the logical way to proceed.
However, I feel that your problem is not with Andrew's sitemapxml mod but appears to be a memory or max execution time problem. After all you have a fair number of files to deal with when executing sitemapxml - a number your server may not be configured to deal with.
You can shortcircuit the lot by creating a file named php.ini and upload this file to the root of your (virtual?) server.
That php.ini file should look like this:
max_execution_time = 30
max_input_time = 60
memory_limit = 128M
set permissions to read only for everyone
Effectively that file overrides the stated values of the native php.ini file (the one that comes with your php server install)
You can see the changes by checking Admin > Tools > Server/Version Info before and after uploading this file.
Alternatively (and that is the safer method) you can add this to your root .htaccess file:
php_value max_execution_time = 30
php_value max_input_time = 60
php_value memory_limit = 128M
Let us know how this pans out.
Cheers / Frank