> - As there was an old gds32.dll. Did you completely
> deinstall Firebird 1.0 before installing Firebird 1.5?
>
> - Are you running Firebird on a different port than
> 3050?
>
> - Are there several (different) versions of gds32.dll
> on your computer?
>
>

I'd overwritten every version of gds32.dll on my machine and it still
didn't work. In the end I uninstalled firebird, deleted every gds32.dll
on the machine, manually deleted the firebird directory and deleted all
references to Firebird from the registry.
Just installed 1.5.0 and it's working! Wahoo!

Thanks for your help.

JD