Intermittent latency during recording

Hello,

I recently upgraded to Sonar Platinum and am experiencing intermittent latency when tracking my vocals with just a single stereo backing track. I have a new PC I bought with quad core 2.41ghz Pentium proc, 4gb ram and using a Lexicon Omega interface. I am using direct interface monitoring with input monitoring disabled in Sonar, and while recording, the timing of the recorded vocal track drifts in and out of time causing synchronization issues.

The pc is running Windows 8.1, and I see that memory utilization is roughly 50% during playback and recording.

Have any of you encountered this, and if so, how did you resolve? I am looking to increase RAM to 8gb, but wanted to poll the forum for thoughts.

Thanks in advance!

When you say "new PC" that's a warning flag. A lot of off-the-shelf PCs come loaded with bloatware (i.e., trial versions of Norton utilities), have unneeded drivers, and load lots of unnecessary routines at startup which eat memory. Memory utilization of 50% while recording vocals with a single stereo backing track seems way out of line, even with 4 GB of RAM (which I would consider to be the minimum requirement these days for a DAW). 
 
Often these kinds of computers, particularly laptops, lead to "SONAR is doing strange things" threads where eventually, the community finds the source of the problem and slims the computer down. If you're comfortable with Device Manager, try disabling drivers for things you don't need (particularly the one mentioned in Tip 35 in my Tip of the Week thread). Also check out the startup programs in msconfig and uncheck the ones you don't need. That should help get the optimization process started. Finally, make sure you have the latest v2.7 drivers for the Lexicon Omega.
 
What is your latency setting? Are you using ASIO?

Bigtime575
Additionally, I am working to tune my OS and startup to strip it down. Any known issues with running real time virus scanners? I am thinking to modify my profile to disable this when I am running Sonar.

Real-time virus scanners can get in the way. Generally I disable things that scan when running a DAW, although often these programs are smart enough to leave the system alone if something is going on.

Bigtime575
One other bit of info. I hear slight audio drop out of the backing track during recording of vocals which seems to coincide with the delays. Thoughts?

That would be pretty much the only way two audio tracks being recorded/played back using the same interface clock could get out of sync without there being a lot of distortion at some point. Errors with plugin delay compensation or record latency compensation could cause a fixed offset during recording or playback but not a variable one.
 
Just to be sure about the clocking, check that Record and Playback Timing Masters are both set to Omega drivers in Preferences > audio > Driver Settings.