site Map Error

hi
please help Me
SiteMap error
* The building process might still be active! Reload the page in a few seconds and check if something has changed.
* The last run didn’t finish! Maybe you can raise the memory or time limit for PHP scripts. Learn more
* The last known memory usage of the script was 11MB, the limit of your server is 64M.
* The last known execution time of the script was 0.4 seconds, the limit of your server is 180 seconds.
* The script stopped around post number 876 (+/- 100)
* If you changed something on your server or blog, you should rebuild the sitemap manually.
* If you encounter any problems with the build process you can use the debug function to get more information.