Fatal error: Allowed memory size of XXX bytes exhausted (tried to allocate YY bytes) in ...
This is not directly related with CB, but depending on the CB plugins and other components you have installed you might see an error message like:
Fatal error: Allowed memory size of XXXXXXX bytes exhausted (tried to allocate YYYYY bytes) in ....
First of all, do not trust your PHP settings, but check the real number displayed in XXXXXXX above. E.g. 32 MB means 33,554,432 bytes, but would be displayed 33554432. Take the time to count correctly the digits displayed in the error. Happened to us too to miscount and search further !
You would need to increase your memory settings in your php.ini file. If you cannot do this on your own then please ask your host provider to do this for you. Google will also help you on this one.
Depending on your plugins, 32 MB or more might be required.
Nice resource regarding process to follow: http://www.ducea.com/2008/02/14/increase-php-memory-limit/
Another Apache param used by some hosters:
http://www.joomlapolis.com/forum/88-usage/99883-solved-php-fatal-error-out-of-memory#100154