I noticed when I hit our messageboard with a mobile device (the windows 7 phone emulator does it as well) that the app pool for the site was restarting. Turns out that I'm getting a System.StackOverflowException.
It looks to me like maybe there is a loop in the code. If I place a breakpoint in the YafContext.cs class at line 164 (inside the get for the YafBoardSettings) I noticed it gets called over and over. The call stack also keeps growing with every couple of runs.
1.9.5.5 Beta (Build 4580)
cschear attached the following image(s):