Session Drummer & Loops

I have to suspect your setup. SD2 should be in sync with whatever parameters you have set.
What sound card/ interface are you using?
Are there audio tracks in your project?
If so, does your project BPM match the tempo of the audio tracks?
Are you dragging the loops to a MIDI track?
Tell us what you can about your system. The more detail you can offer, the better.

Sorry for the delay, but I'm finally getting back to this.
I never use the media browser, so I had to spend some time with it.
You're right. a lot of those loops are pretty generic, and I'm not really sure where they are coming from.
Use the Program files included with Session Drummer. I think you'll like them a lot better.
When you insert SD2 into your project, select the following options:
MIDI Source Track
First Synth Audio Output ( you can select All Synth Audio Outs later, but keep it simple for now).
Synth Properties Page. This is the SD2 GUI, and you'll need it to access the program files and control your drums.
Each group of 8 patterns include variations on the basic theme, plus a few fills.
Click and drag on the note icon to pull a selected pattern to your MIDI track.
You can build a fairly interesting track this way. The MIDI track can be edited further in the PRV.
 
I need to clarify this a bit:
"Project has several audio tracks (both instrumental & vocal).  Didn't know that track BPM could differ from project BPM but hadn't messed with it and haven't seen that problem before."
 
You can't specify different BPM for the tracks. However, audio tracks don't necessarily follow the project BPM.
A MIDI track will explicitly follow project BPM.
If your project is set to 120 BPM, that is what the MIDI track will play.
If your audio track happens to be 110 BPM, it will make the drums sound decidedly asynchronous.
It's best to do the drums first, or at least have a click track set to the project when recording your audio.
It is much easier to sing/ play along with the project clock than it is to try to sync the project to an audio track.
 
As to the dropouts and irregular performance, that is most likely the Realtek. It is fine for basic playback, but does not handle the more complex demands that DAWs put on it very well.
A decent interface can be had for $200-300, and will be the most significant investment you can make for your studio. It will make a huge difference.
Hope that helps.
 

You won't have very good results until you purchase a audio interface, You need the stable drivers to have good timing. I tried to use an on board sound card the other day and I realized how terrible it really is. Hit the GUI drum skins and hear the note play at least a second later.. not good. This is what you are experiencing, Sonar clock source will be set to the Real tech. This is problem. 

Cactus, you may be right about the sound card.  I downloaded a midi loop with a good steady rhythm.  Played it on my Sonar and it sounded lame and disjointed.  Exported it to an MP3 file and it played back fine.  Therefore, something in my set-up is keeping Sonar from playing the whole drum loop properly.

http://www.roland.com/support/article/?q=downloads&p=BR-80
 
 
 
Here's the drivers..