I had "client-type=advanced," specified and couldn't get a work unit that would, well, work. Dropped the advanced option, able to work.
Here are the units that won't start on the AMD V7900:
project:14201 run:417 clone:4 gen:0 core:0x22 unit:0x00000000cedfaa925eb99bba95257ba4
project:14201 run:276 clone:0 gen:12 core:0x22 unit:0x00000012cedfaa925eb99bba666672f8
Here's a unit that works (non-advanced):
00:53:27:WU02:FS01:0x22:Project: 11763 (Run 0, Clone 10247, Gen 40)
00:53:27:WU02:FS01:0x22:Unit: 0x0000005c80fccb0a5e7113460ed95a97