"The man with two clocks doesn't know what time it is" principle applies here.
You are attempting to clock one sound card from another without locking the audio clocks together. Sooner or later, something is "going to give," and one card will either under or over clock the other, and start to audio glitch.
This is also what is very carefully controlled in a true audio over IP network environment, if implemented correctly.
To solve the original problem here, I urge you to use the correct Optimod-PC cable and use just the one sound card.
The pin out of the 1101 connector is very conveniently on the cover of the 1101 card if you would like to "roll your own" cable assembly.
If you do need to lock more than one sound card together, you can do so by using either AES or Word Clock and connecting all the sound cards to the same clock source. This requires all sound cards to have this capability, which most professional cards do. Some semi-pro cards, such as M-Audio may be clocked using S/PDIF inputs and clocking from that input rather than Internal.
Hope this helps clarify this.
-greg.