First of all, I'd urge you to try another mouse. Thunderbird seems to be unusually sensitive to a dirty click, as happens with a high mileage or poor quality mouse.

I don't think anything has fundamentally changed in the presentation of messages, so can you describe in more detail or provide a screen shot and help us understand what you mean by a "more complex layout"? You can almost certainly go back to what you are accustomed to but I doubt it has any bearing on the multiple issues you mention.

It does appear to be a mouse problem. I recently stripped and cleaned my PC and peripherals; fiddling with the mouse yesterday, there appears to be a loose connection between mouse and cable giving possible double clicks; I'll get a new one and see how I go.. The recent change to T'bird I referred to was the update that introduced extra columns in the main frame list of messages showing recipient and other detail I had not seen before or need. I firmly believe in using programs as simply as possible as "bells and whistles" fog the essentials. But then again I am an old fogey! Thank you. JH

A new mouse seems to have fully resolved my problems. Thank you Zenos!