Lightroom opens all of a sudden with a message stating "you already have Lightroom Catalog open ....Close the other version of Lightroom???? Never happened before, And windows task master says I have no other lighroom open?
The message says you have a CATALOG open.
What it means is that the last time you used Lightroom you did not close Lightroom in the correct manner and it left the CATALOG in a 'locked' state. Maybe the computer crashed, or you just switched it off?
First -know where your catalog is stored.
Open explorer/finder at your CATALOG location and delete the file that has a name that ends with "....lrcat.lock"
Do not delete anything else! Do NOT delete the file ending with "...lrcat" (that is your catalog with all your work!)
Then restart lightroom.
The .lock file is a temporary file that is always created when you open a catalog with Lightroom, to prevent multiple users opening the same catalog at the same time.