The link to the thread
http://www.volvoforums.org.uk/showthread.php?t=221555
To sum it up, the D4 VEA is a relatively new engine and as such there have been some teething issues affecting a number of cars this exact number is not clear, dealers and Volvo would have you think yours is the only one. It's not lots of people have had this issue but not everybody.
It seems the most common fault is the egr cooler which it appears leaks I assume it's linked to the engine cooling to cool the exhaust gas, so this small leak of coolant mixes with the exhaust forming a paste which blocks the egr valve causing a fault to be logged.
The fix now seems to be to replace the egr cooler with a slightly updated design which should address the leak, there have also been software updates which some owners have reported effect the performance.
I have had my cooler replaced and the new software installed and have noticed no difference in performance, my car is an early car so one of the first with the 190 tune of the D4.
Most egr cooler problems seemed to read there head at around 10k miles out of interest what was yours on?