Ok got it sorted - yay me
Solution was to do the following (on a machine running WIndows XP, Apache 2 and the updating to latest version of PHP 4.3.11)
1) Uninstall older version of PHP
2) Completely remove all files in your php folder
3)Install new version of PHP - I used the windows installer, then downloaded the windows zip file and copied in the extensions, etc
4) Make sure new/update version of php.ini is in your Windows folder
5) Backup php4ts.dll that is in your apache folder - then from your php folder copy the latest version of php4ts.dll to apache/bin (search for your apache.exe file and place the dll in there)
Restart apache (you may need to restart your machine) and it should work ok.
If anyone needs a dig out - keep this thread alive (maybe the mods can make this a sticky as it seems to be a re-occuring problem)