I do not have a easy answer for you, but I use the latest M-audio drivers with an old MobilePre USB(16bit/48Khz max), and I can only say what I have observed..
The drivers and "card" work great "crackle -free" at a not to low latency (512), even with the Cori Yarckin project playing in X1 and one of the bigger test projects in Project 5 v2. I use a i3-2100 CPU with 4Gb and Windows 7, 32 bit. However - I noticed when I do exactly the same on the same computer (I use a multi-boot configuration) in Windows 7, 64bit - the card starts to crackle and I even get drop outs. This happens in X1, Project 5 and even in Protools 8 M-powered (to make sure this is no Cakewalk-only problem). I have to increase the latency buffer to 2048 to get at least a acceptable sound out of it, but it is still unstable. This leads to my conclusion there is definitely something wrong with the drivers in 64 bit. Do notice however this is my experience, this does not have to represent the experience of all users.
I also tested the E-MU 0404 PCI, M-audio Audiophile 24/96 PCI and ESI Juli@ PCI cards in exactly the same computer, and the same applications, and they where working without any problem on low latency (2,5 ms/128) in Windows 7 32, and 64 bit and in all those applications, so I am inclined to say you can rule out the Cakewalk software as the culprit.
Now - I know the MobilePre is an older card than you are using, but the drivers are at least the same. That can lead to the conclusion the problems lies within the combination drivers/Windows 7 64 bit.