When switching between any two or more Vim tabs, the cursor is reset to the first row and first column, regardless of where the cursor was prior to the switch.
To repeat:
Open two files with vimplugin.
Click first tab and move cursor to any position other than 1,1.
Click second tab and move cursor to any position other than 1,1.
Click first tab again and note cursor position.
Logged In: YES
user_id=53674
Originator: YES
It appears that if you quit Vim with :q the cursor remains in its original position in the other window.