I had an old (old) version of BBTetris (version 1) I think but I deleted that. I've also tried downloading it and installing it from my SD card. Unfortunately I still get the same result.
FYI I'm running with OS 5.0.0.979 if that's of any use.
I can maybe generate a .alx + .cod sometime later.
There shouldn't be any conflicts. Nothing else uses the same module names. The only time I've ever seen the 907 error is if I tried a local install if the game was already installed.
FYI I'm planning to wipe my device and install a hybrid; what I'll try and do is install it first thing to see of that helps. The only unfortunate thing (for me) is that I won't be able to do it until the weekend. I just don't have the time.
Anyway, thank you so much for your help. It's much appreciated.