Mac Pro and FireWire external sound cards problems

hello!

I got my Mac Pro for several days, and I'm trying to start my work with music. But I got a problem
and have no idea how to deal with it.

I got two FireWire sound cards - MOTU Traveler and TC Konnekt 24D - all of them working
perfectly under PC. Have downloaded and installed all updates to Mac OS X and latest drivers
for those sound cards. When I'm plugging them to my Mac Pro - they appear normally - i mean
software bundled with drivers indicates that cards are present. But when I'm trying to do some
playback actions through MOTU or TC (i never using them together - only separately) - it seems
like they are out of synch with firewire - they begin to do some weird things. for example
TC Konnekt 24D - indicates that device is out of sync, and MOTU Traveler - just producing some
ultra-high frequency low-volume noise and that's all. Have tested that in several programs,
Logic, Bias Peak and etc. If i will try to turn-off and then turn-on those cards several times -
sometime i got them to function normally. But 90% of the time they do not work correctly.
All the firmware versions in these cards are up to date, also i've used latest driver versions for
both.

I found something strange in my System Profiler, under the FireWire subcategory:

*FireWire Bus:*

Maximum Speed: Up to 800 Mb/sec

*Built-in Hub:*

Manufacturer: Unknown
Model: Unknown
Maximum Speed: Up to 800 Mb/sec
Connection Speed: Unknown

Vendor 0x1F2 Device 0x107800:

Manufacturer: 0x1F2
Model: 0x107800
GUID: 0x1F2000001966F
Maximum Speed: Up to 400 Mb/sec
Connection Speed: Up to 400 Mb/sec
Sub-units:
Unknown Unit:
Unit Software Version: 0x9
Unit Spec ID: 0x1F2

is that normal?
is it possible that my firewire drivers are broken?

I've also tested those cards with regular PC computer - all working excellent at all samplerates,
buffer-sizes and etc.