I've been using Sonar 8.5 Producer for over a year with the same problem. I run W7 64 bit and Edirol Fa-66 (fire wire version of Ua25ex.  For the first several months I was using the WDM/KS and when it wouldn't dropout, the timing would fall off throughout the project. I would swear I was dead on with the click during recording, but when played back it would progressively fall off time. I finally switched to Asio mode driver and thought I had the problem beat, the timing was there and all. After a busy month away from recording, I tried to get after it again today, but, no. Dropouts, interface and hair! An issue I have also, is when you turn your computer on, you must not have the interface plugged in or turned on. It seems like if you don't plug the interface and power it up at a specific "get lucky" time after log on, it won't recognize the interface. In fact, I won't even open sonar until I go into my control panel under sounds and see if Fa-66 is listed. And even when it is not (most of the time), I can go in under devices where it is listed as working properly.  Sure seems like a driver issue to me. I recently added a A-500 Pro midi keyboard to my set up and that works without any issues at all. I read all the posts about settings, latency and buffers, etc. Yes, I do also have the 64 bit driver loaded for Fa-66. I think I'll try a newer USB interface with, hopefully a more stable driver.

Hp DV7 AMD Turion II Ultra Dual Core M620 2.5GHZ 4.0GB RAM W7 64bit 500GB Hardrive.

  Here are some of the things I've tried lately... I'm using the latest drivers for UA25-EX and latest update of Cakewalk 8.5. By the way there seems to be only a version 1.0 for the UA25-EX. Computer is a Frost, brand new, made specifically for music production. Company says Sonar should be perfect on this machine. It’s clean on delivery, no drivers are pre-installed, not hundreds of extra freeware gadgets that popup as tray icons, operating system is optimised for use with music production software. Windows 7 64 is updated with latest patches – no difference before they were installed, no difference after, it all works fine for 3-4 minutes then no sound. I’ve tried wireless mouse and wired – no difference, it all works fine for 3-4 minutes then it stops. I’ve tried connected to network and not connected, even tried to turn off wireless network adapters – no difference, works for a while then no sound. I’ve tried five different USB cables for the UE25-EX, shielded and unshielded – no difference. There is no antivirus on the computer – I’ve tried with antivirus as well – no difference. I have tried to uninstall/reinstall the sound interface drivers at least 20 times, strictly following Cakewalks setup procedures. I’ve even tried to install the 32-bit drivers and realized it’s a pointless suggestion that you shouldn’t do this - simply because you can’t install them on a 64-bit system – no difference. I have followed the audio setup procedure suggested by Cakewalk support. I have also tried to use WDM/KS and some of the others, even though Cakewalk support suggests ASIO – no difference. I have tried all the different sample rates, using the same sample rates in Sonar as on the UA25-EX – no difference. I have not tried to install on another system but obviously other people have done that and it has worked for them. However, I have tried to use a friend’s UA25-EX just to verify there’s nothing wrong with my particular interface, my interfaces also works fine on his system – so, no difference. I really love Cakewalk and the functions in it, but I’m seriously beginning to think I’ve selected the wrong products.

I've just installed Sonar x1 to my computer...hp pavilion....about 4yrs old, 32bit vista. I hooked up the AU-25ex interface and everything seems to work except the headphones. Not sure what to do, perhaps re-install the driver. Any others have this problem? Any solution? Newbie here.

I've solved the problem of separating the headphone level and monitor level. Now I'm getting pops and crackles. The driver version is 1.1.1 for the ua-25ex. Is that the latest? How do I find out?