This message means that another user is running the Q++Updater. No user can use Q++ while it is being updated, so you should :
|1.||Wait until that user is finished updating Q++|
|2.||Apply the update to your PC|
|3.||Launch Q++ again|
If you think that this message is incorrect (ie. noone else is updating Q++), then go to the Q++ServerXE2 folder and delete the file updater.flg, before trying to launch Q++ again.