LynxTWO sounding too sharp and having no lows

At first I thought it might have to do with Nuendo, and for a time I tried to compensate for it. Then I realized for sure that the simple audio-cutter I use for editing field recordings sounds more or less the same, so the problem obviously must reside in the computer, card, or system. Come to think of it, I remember when upgrading the system from XP to Win 8 (64) the first place I did notice a change in sound. What gives here you reckon?

I can't remember how it sounded before, but though the LynxTWO-card does indeed seem to fight with my BlackMagic Intensity-card, I don't think the sound went weird when I installed the video-card, but I know for a fact that I reacted to the more detailed sound in Win 8 Pro.
I tried to remove an option called "Topology Driver" in the settings, and I THINK that did the trick for a while! But I'm not sure. Might have been stress-ears talking there, but I actually think it worked for a while.
Not now though. Whenever I try to disengage it, the computer flips me the bird and turn it on instantly again.

For reference, this is mah gear here (haha): PC with last generation Intel Core2Dou/Gigabyte motherboard, LynxTWO, Intensity Pro PCI, Windows 8.1 Pro, Nuendo 7. Granted I do not know how the sound-engine of a soundcard works, I might have missed something that affects the sound, if so, do tell & I'll find out what I have.
I can work with this, have done several big gigs on this system since the upgrade, but it's very frustrating and takes time, and everything else is awesome otherwise. Surely there must be a way to get the system totally bit-transparent?

Thanks in advance, Christian van Caine

I actually managed to fix this eventually. I have no clue why this happened, but while combing through the system after what it was making my poor card acting this way, I realized there was an option called "Show hidden devices" in the window where I choose what soundcard output to use for the system. I checked it and...suddenly I saw a new thingy called something like "Lynx Sound Device" or similar (my system is in Swedish whether I want it to or not, but roughly translated). And it was disabled.

I enabled it and...presto - problem solved! The sound I knew and loved was back in all its meaty and balanced glory!

Weird thing is, before that I made numerous different tests to figure out what was wrong, and recording AES/EBU Digital Out directly short-circuited to Digital In first resulted in a completely flat response in Room EQ Wizard set to ASIO, then later to a very tilted one. I couldn't test it in S P/DIF as I don't know where my adapter cable for Digital In hides right now, but I bluntly assume there shouldn't be much difference. I can't remember which one I did an internal routing on in the Lynx Mixer, I was pretty stressed, but I assume it might have been one the tilted ones (did a lot of tests). Trying to set REW to Windows native drivers made the entire system fritz out completely on scanning.
Not counting that Nuendo never has been WYHIWYG (though pretty close in version 7), trying to record audio in the regretfully only Windows-driver-capable WaveShop still gives pretty weird results, and I have no clue if I still have remnants of the problems I had before, or if this is related to the program itself - I have no way of testing that right now - but in short, trying to record something in 96 or 192KHz 24-bit makes the Lynx Mixer telling me it's really set to 44.1KHz/16-bit, and judging by the sound, it isn't lying....
Playback seems to jive well though!

I now know for sure that it is neither Nuendo nor Windows that acts up on me, to be able to finish my current gig I had to switch to an old Firewire Focusrite-card (box), and with the exact same monitoring system, the problem is gone for now.

One thing I noticed when trying to work with this card is that the sound sounds like there was some kind of extremely high-frequent phasing in it of a kind I've never heard nor heard of before. It seems to act much like some kind of exciter, while scooping and mudding up the higher low-end a lot. It is also in that area that the phasing is really identifiable, though it also makes filter-sweeps pretty interesting. I can't examine this closer until this job is done, but my impression of the sound is that it sounds like two totally identical signals in tandem with only samples delay between them, and no feedback at all. Audio mainly in high frequencies sounds extremely clear, but anything even remotely fat sounds damaged.
Of course I make sure to listen to the sound without allowing any form of loopback patching, neither from the input channels nor via the programs outputs, though it does sounds like the phasing might be depending on both processor-load and whether it's ASIO or DirectSound.