I had a very nasty indicent - it was not an Airbus but another highly automated fly-by-wire aircraft (SB20). There was a lot of slush on the runway, which was sprayed onto the lower side of the fuselage, some chunks of it must have frozen and stuck to the radio altimeter antennas.
We didn't find out until approaching destination. As soon as we lowered gear, GPWS didn't stopp yelling. Since we were severely CAVOK and had no other warning, we figured out that it must have been a nuissance.
I'm not sure now if we also found out that radio altimeter always stayed at zero height.
Dani