Yes, that sounds logical.
I installed the 10.9.4 Combu update, still the same problem though
I will try to remove iTunes, and install it again...
Edit:
I did some testing...
I have Indigo 5.1.10 running on a Mac mini Core2Duo 2.66 GHz with 4 GB RAM, running mavericks 10.9.4 and Server app.
I have iTunes 11.3 running on Mac mini Core2Duo 2.4 GHz with 8 GB RAM, running mavericks 10.9.4.
When entering the 4digit code iTunes crash within a few seconds.
Removing the iTunes.app directory, installing the 10.9.4 combo update, reinstalling iTunes, same result.
Trying on the Indigo computer, iTunes crash there too.
Trying on my 2.4 GHz machine logged in as a Guest, iTunes crash...
So do you think it will help to upgrade to Indigo 6? I know Apple has changed iTunes 11, so maybe Indigo 5 doesn't work then? But it shouldn't crash, but that could be an Apple bug...