I seem to have fixed this. For information, here's what I did ....

- In IIS properties/home directory change the application protection
from it's current setting (probably pooled) to something else.

- In IIS properties/home directory/configuration untick the cache
tick-box.

- Stop and start IIS

- In IIS properties/home directory change the application protection
back to it's previous setting (probably pooled).

- In IIS properties/home directory/configuration tick the cache
tick-box.

- Stop and start IIS


It worked !! I don't know how or why, maybe something was reset.

Note this problem was experienced when using IIS with PHP4 and 5.0.2
with MySQl and MySQLi with ISAPI. CGI seemed to work OK.

Hope this helps someone.