[roann]

Originally Posted by GRC

Yup, I was beginning to suspect that - could I have changed anything, like a user-accessible folder option, that's triggered this behaviour? ...

No.

Originally Posted by GRC

... Since the iTunes add folder dialogue was working OK before, and it seems to have changed its behaviour since the TLH installation, could there be any element of the TLH install itself (rather than the running program) that could have affected it...?

No, TLH just calls a given Windows OS routine (as I said before). This has absolutely nothing to do with the installation process.