Hi there, thanks for posting.

The alt-tabbing issue is well known.  From the roundup:

Map does not render after alt-tab (1) (2) (3) (4) (5) (6) (7)

For the future, please read the stickied beta reporting guidelines before posting.  Not following the guidelines will probably get your post further down on priorities, if not completetly ignored.  It at least makes Kryo sad . At the very least, your post needs a title label and a version number.

Also, have a look at the beta roundup to see if your issue has already been mentioned (less duplicates == better ).