Ubuntu 10.04 - php5 cgi all of a sudden causing cpu spikes

Hi, I would be very grateful if somebody would help me with this as I am not very experienced at server administration.

I am running Apache web server and recently cpu usage has been continually spiking, whenever I look at htop php5-cgi is using a large percentage of cpu time on all four cores.

This used to be caused by google pagespeed mod, but I am not currently running this mod.

I am wondering if this could be caused by a recent update?

Currently traffic has dropped off due to a google algorithm change, so I am receiving only 1/2 as much traffic as before.

Any ideas/help would be much appreciated.

Thank you in advance.