re0 watchdog timeout and high interrupts

My laptop worked fine at 4.2. I tried several snapshots of -current
and all had the problem:

Poor network performance and a sluggish system. Iostat showed 65%
interrupts. The log shows
re0: watchdog timeout every 10 minutes.

The 4.3 beta snapshot works better than earlier snapshots, but is
still showing these symptoms. Are there any ideas re: cause or
solution?
.