*** glibc detected *** double free or corruption: 0x0811fd30 ***
That ladies and gentlemen is the mysterious error that you pops up when attempting to start up apache. The error was first noticed after compiling php5 with the tidy extension. Apparently this has something to do with memory allocation. A couple of make cleans followed up fresh compilations didn't seem to solve the problem at all. Then I switched back to 4.3.8 but suprisingly the error message refused to clear up.
The typical reaction of a windows user when faced with this kind of situation would be to restart the machine, my soul cringed at the tought, but then I found a face saving solution; I had to go out to visit a friend and you will agree that it's perfectly ok to shutdown a computer when you leave the house.
Unfortunately on rebooting on my return I find that the error message has not gone away. It was then that the realization dawned on me that I have been pretty stupid. When installing php 5 it had created it's own LoadModule entry in the httpd.conf file and now there was a conflict between the to SOs.