Marcia Smith has a report on the anomaly analysis for the SpaceX station resupply mission:

Several other problems also arose during the mission. While berthed to the ISS, one of the three computers on the Dragon spacecraft failed. Dragon can operate with only two computers, and SpaceX chose to proceed with the two functioning units rather than trying to fix the faulty unit while on orbit. According to Suffredini’s charts, Flight Computer-B “de-synched” from the other two “due to a suspected radiation hit” and although it was rebooted successfully, it was “not resynched.” Dragon experienced other anomalies because of radiation as well. One of three GPS units, the Propulsion and Trunk computers and Ethernet switch all experienced “suspected radiation hits,” but all were recovered after a power cycle. Suffredini said that SpaceX is considering whether it needs to use radiation-hardened parts instead, but noted that “rad-hardened” computers, for example, not only are more expensive, but slower. He speculated that the company would ultimately decide to use rad-hardened components in the future unless it is cost-prohibitive.

I had heard that there were also SEUs on the first ISS flight. It’s a young system, with very few actual flights, which is how you learn about things like this. But clearly it has enough redundancy for mission success (including in its ascent propulsion system). There’s a trade between using rad-hard components and utilizing more shielding. I assume that SpaceX is doing that trade right now (and perhaps has been doing so for months).