If you specify a pdf viewer via AlphaCocoa>Global Setup>Helper Applications... then it is not picked up when one enters TeX mode. It seems to me that if no app has been hosen in the mode then the default should be what has been specified globally rather than Acrobat, which seems to be the default becauseit is the first item in the list.
This is the consequence of a deeper bug found in the xserv machinery. The xhelper dialog type returned a wrongly formatted value (it expects a dictionary describing the chosen implementation).
This is fixed now.
Changes committed to svn (rev. 1083).
This can be closed.
Closing now.