I'm having a similar problem. I'm still searching to resolve, I'll update here if I find anything.
Here's what I have and what I've tried -
double 7870 GE setup
Asus 750W PSU
ASUS Sabertooth 990fx RA.2
Xubuntu 12.10
cgminer 3.0.0
Latest AMD/ATI drivers
I get the same GPU output in terms of GPU#1 stuck at 300/150:
GPU 0: 197.1 / 196.6 Mh/s | A:21 R:0 HW:0 U:2.33/m I:9
69.0 C F: 83% (5325 RPM) E: 1100 MHz M: 1200 Mhz V: 1.219V A: 99% P: 20%
Last initialised: [2013-04-23 23:14:57]
Intensity: 9
Thread 0: 99.0 Mh/s Enabled ALIVE
Thread 1: 98.3 Mh/s Enabled ALIVE
GPU 1: 193.0 / 196.2 Mh/s | A:28 R:0 HW:0 U:3.11/m I:9
31.0 C F: 83% (5291 RPM) E: 300 MHz M: 150 Mhz V: 0.825V A: 0% P: 20%
Last initialised: [2013-04-23 23:14:57]
Intensity: 9
Thread 2: 96.1 Mh/s Enabled ALIVE
Thread 3: 96.4 Mh/s Enabled ALIVE
my question really is, is this cgminer config issue or drivers? almost tempted to dualboot/install windows with guiminer and test.