Tip dissapear on first ajax loading

techwell.vps-private.net/

under logo, there are 2 links.
both are calling to the same block #unisender_block via ajax

BT is fired on click

after click on link, BT is loading, content is displayed and..dissapear.

after click again, is displayed without any problem.

so, there is the bug? why ajax content dissapear on first click?