Icedove does not open messages on double-click??

[Dennis Wicks <wix@mgssub.com>]

Greetings;

I am running fairly vanilla Jessie 8.1 and now Icedove does 
not open messages on double-click, only on <enter>, at least 
90% of the time anyway.

And "F" does not go to the next message unless the current 
one was opened with double-click.

Any hints, tips, etc.?

TIA!
Dennis