trouble with php4, apache, egroupware, memory allocation

[Mark Busby]

I'm running apache-1.3.37_4, php4-4.4.7, and eGroupWare-1.2.106_1. 
  Apache error file is returning the following error when trying to access the calendar.
  PHP Fatal error:  Allowed memory size of 16777216 bytes exhausted (tried to allocate 23040 bytes) I've searched but have not found a working fix. 
  Any Ideas??