First of all thanks for this great ROM!
I've just flashed CM 12.1 to my P5110 (the Jan. 29 build), and everything seems to work fine so far. I just cannot connect the device to my PC via USB.
I have enabled developer's options and USB debugging. When I connect my tablet to my Windows 7 PC, nothing will happen. When I open settings > storage on the tablet, there is a menu in the right upper corner showing "USB-Verbindung (PC)" (USB connection (PC)). But when I tap this option, a message will pop up saying that the USB connection will be disconnected. The same will happen if the cable isn't connected at all.
Thanks in advance