It would be impossible for outsiders to calculate the failure rate because we have no way to count how many BMWs have this complaint---only BMW would know this.
There are, however, numerous TSBs issued to dealers over the years about various failures related directly or indirectly to the CCC (sometimes it's not the CCC, but the hard drive, or the MOST-bus, or cabling, etc) and some of them do directly deal with CCC failure
Here's one example of a TSB indicating an outright CCC failure, which may or may not relate to your particular problem:
SI B65 47 05
Audio, Navigation, Monitors, Alarms, SRS
This Service Information bulletin supersedes SI B65 47 05 dated March 2006.
[NEW] designates changes to this revision
CCC - CID Switches between BMW Banner and Blank Screen
E90, E91, E92, E93 (3 Series) with SA 609 Car Communication Computer (CCC)
E60, E61 (5 Series) with SA 609 Car Communication Computer (CCC)
E63, E64 (6 Series)
E70 (X5) with SA 609 Car Communication Computer (CCC)
[NEW] Vehicles produced up to 3/2008
Keep in mind that these are not recalls--more like "heads up" for the dealers to help them solve problems. Of course, the TSBs state that within warranty, the defect would be covered.
If you're out of warranty, it's strictly a matter of a good will adjustment at this point. BMW isn't legally obligated to help you anymore but if you mention that you know about all the CCC troubles, perhaps they, or the dealer, will do something for you.
I think this is a fairly pricey part, something like $600?