Solving ASIO problems using Terratec DMX6Fire 24/96 soundcards

Drivers
A general advise regarding drivers: If you use the DMX6Fire 24/96 card, please use the driver revision pack 5.40.128 and not the 5.40.130 or 129 since this version has a lot more issues regarding ASIO control. (e.g. un-unlockable samplerate in the master-clock table and if worse:spontaneous reboots during switch-attempts from ASIO to Direct Sound)

General problem
If you own a Terratec DMX6Fire 24/96 card, there is a chance that your audio-drivers lock up once you have activated ASIO and attempt to switch back to Direct Sound. To enable Direct Sound support you have to reboot Windows completely to fix this problem. This is a problem that occurs in any host that supports ASIO 2.0 drivers and has nothing to do with Renoise. The advise for installing the card in the lowest (or a different than the one where the problems occur) PCI slot may work out for some but unfortunately not everybody. Another advise is to switch off any embedded mainboard audio device you can disabled in the system BIOS if not there, just disable it in the Windows Device manager. Check your IRQ and DMA shares (msinfo32.exe) and see if you can reroute some of them to other resources. Remove unused devices that use an IRQ /DMA share with your Terratec device. It may not resolve the problem completely but could bring down the instability (and increase the performance) of the Terratec Driver.

DMX 6Fire issues regarding Renoise not being able to toggle Direct Sound drivers after using ASIO drivers
If you shut down Renoise previously using ASIO drivers, Renoise will reuse ASIO drivers when opening it the next session and since the audio-driver lockup may prevent switching back to Direct Sound and completely locking up Renoise, the only way to toggle this switch is to open up the configuration file (c:\documents and settings\[username]\application data\Renoise\V1.5\Config.xml) and locate the following header:

<!--Audio IO-->

Underneath there change the following line
<Property name="mActiveDeviceType" value="1"/>
To:
<Property name="mActiveDeviceType" value="0"/>

Save the file when you are done.
You are advised to make this change before you start Renoise (but actually ANY host that uses ASIO).
If you have started Renoise in ASIO mode, reboot prior to starting up Renoise.
In the best situation, you can switch back to Direct Sound without locking up your audio-application but the ASIO driver will not be released. In that case, switch back to the ASIO driver before closing Renoise, then close Renoise, change the value in the Config.xml file and start up Renoise.
This is the only case where (if lucky) you do not require a complete reboot of your PC.