No feature codes when Music On Hold is enabled!

Hello to each one of you,

i have a weird problem here in my FreePBX system. I use FreePBX the latest FreePBX Stable version. FreePBX 2.11 and Asterisk 11.

I have a Dahdi card with 3 extensions and 1 Sip extension for a soft phone.

The weird thing is that when i choose from Follow Me settings of an extension, the option Play Music On Hold? other than Ring, then i cannot transfer the call. (I press my feature code for In-Call Asterisk Attended Transfer and nothing happens. I hear the beeps of the keys pressed).

If i switch the Play Music On Hold? option to Ring, then everything is working!

What do you think may happening ?