Thanks Petertron5000,
I'd already figured that quitting it in the one account and running it in the other got round my first problem, it also happens to cure the second.
However, whilst I appreciate the suggestion, I see this as more of a work-around than a fix. I don't see any reason for SD to behave in this way, I've never seen this problem with any other software and it's only happened in the last couple of months. Is this some kind of anti-piracy measure or just some bad coding? Either way, it's an annoyance. I have to quit SD, log into the other account, start SD which can take anything up to 90 seconds, log out the second account and then start SD again in the first accout (another 90 seconds). Why?
Thanks again for the reply though.