HiFIBerry Digi – Linux 3.12 driver issues since May
Raspbian is moving now to Linux 3.12. It looks like the I2C driver has been changed which results in problems detecting the HiFiBerry Digi board. We were able to create a workaround, however for the mainstream kernel we want to make sure that the root cause is fixed. This might take some time as we have to get in touch with other developers.
As a quick fix, you can downgrade to Linux 3.10.38 with the following command (as root on Raspbian):
Update 31.5.: The root cause for the problem is an updated i2c driver from May 16. On May 26 this code has been disabled by default. Therefore rpi-update should work again soon.