Thanks for the reply. This is driving me nuts. Luckily so far it has not affected my actual output, but it is extremely irritating. I have a copy of Sonar 8.5, but not installed. I will give it a go. Thanks I have Win 7 64 Home Prem SP1. I will check for conflicts anyway.

OK. I have installed SONAR 7 Prod and loaded up a song. I have sat (sitten??) here for 5 minutes doing stuff on another PC and it has been as silent as the grave. I have deliberately turned the latency down as far as it will go (5.8ms, 2 buffers). I have tried ASIO , which is what my X1 is set to, and still no clicks. CLUE...I do get one click as I open a project. It is the same click that I get in X1 all the time. One channel, lots of HF/supersonics, I think. I base that last on the fact that it is barely audible, but the meters give a huge jump in the card's mixing programme. I have very good high hearing and can gear "supersonic" (25KHz)alarms in shops sometimes. Not boasting. It's a PITA. But it means if I can hardly hear that spike, it's very high. (Or very fast I guess)

NEXT! (1) If I open X1, then open a project, it clicks as I open the the project, then keeps clicking as long as the project is open. (2) If I then open SONAR 7 and open a file, I get a single click as I open a project, then silence. (3) If I then _close_ SONAR 7, reopen and then load a project, there is NO CLICK. (4) But if I then close SONAR 7, and open SONAR X1, the open a project, it clicks as the project loads, and keeps clicking. NOW. (5) If I then close sonar x1 and reopen SONAR 7 and load a project, I GET THE CLICK AS I OPEN A PROJECT.....See (1)....X1 is doing _something_

then it's probably time to call support CW support on this one.  good luck!

OK. I got onto to support and they suggested a few things like disabling all startup applications (boy! I thought I was getting the PC nice and mean and clean already) and also playing with buffer settings. But what did the trick was resetting the Config file to defaults. Not sure what that has done exactly, but I seem to have some latency there although it's supposed to be 5.8mS. I can actually hear the time between activating a note and its playing. I doubt I could hear 5.8mS and it seems worse than it was before.

so, it wasn't the card, but the system.

http://www.thesycon.de/deu/latency_check.shtml Have you used such a program to check your computer??

@batsbrew "so, it wasn't the card, but the system. " No not the system as such, but how SONAR was set up and interacting with the card. I can't say more (because then I have to kill you :D) because I fixed it by resetting all the Config file settings to default and have no idea what setting did it. Part of the try to fix involved the system, but made no difference to either the SONAR click or the system "plangent bellow" at shut down.

@spacealf "http://www.thesycon.de/deu/latency_check.shtml Have you used such a program to check your computer?? " No, but I will have a good look at it. Thanks

Actually it's interesting, because there seems to be worse latency when I first activate a note on a given instrument, having opened PRV on that instrument, then it's a lot shorter for all subsequent activations. . I am using PRV here, so it's not any sort of external latency.