Strange Temp directory used

[Andreas Paeffgen]

MacOS 10.7.4, Lyx 2.04

In the preferences of Lyx i set the temp directory path to 
/Users/MyUser/Documents/TMP.

But Lyx uses the following path to create tmp files:  
/private/var/folders/c9..........
Is there a way force Lyx to use the path in the preferences?

Andreas