Hi Robur, there are a few things to consider, so please bear with me.
First, the log you posted is awesome - thanks for giving the detail - but it's the 56th error in the !Swatter log, so we might not be looking at the 'right' error. Please logon and in the chatbox type: /swat clear This clears the swatter error log. Then, re-create the problem and post the 1st error entry from swatter so we know where to start.
Now, about BTM... it's been removed from the current Auctioneer suite and it's functionality has been replaced by (and added to) with the newer SearchUI. Information about use of SearchUI is here - it is different as far as how it looks/feels, but you should be able to do everything you did with BTMscan previously.
I feel stupid now. Should have wondered that there was no Bottom Scanner in the latest distribution and should have erased the old version. I blame lack of sleep due to patch drama. On the other hand, BT is easy mode now, we zerged through six bosses in two hours. But I disgress. ;-)
Here's the log, just for kickers - guess it's mainly because BTM isn't really supposed to work with 5.1 anymore, so probably no action needed.
Which you will need to download separately. It's no longer included in the AuctioneerSuite package, as it's going to be replaced by SearchUI, which we recommend you use instead.
I'm also having problems with Alt-clicking and shift-clicking right now, and I don't think it's the Auc Addons that are causing them. I'll try to troubleshoot more later when I can log in again though.
No worries! I actually went through the labour and marked all the things I didn't want to sell invisible/hidden, so now I see only the things I want to sell in the full Appraiser view. While this is somewhat faster than dragging each item into the simple Appraiser view and I bet I can get used to it, I see how many people that might not be as computer savvy might have issues with it.
So I salute you for listening to the community! Much appreciated.
Now, about those bugs. ;-) You're not alone, of course - many add-ons don't work at all or have very weird results. I can't see main tank windows any more and get a weird cooldown window from ora2, for example. But that's another story.
If I can help researching the mystery of the non-working click further, let me know!