Okay, Just went a checked mine (which is the PCR 500-Same as the A-Pro500/800 minus a few keys). 
Hasnt even been set-up on this computer before.
Downloaded Driver for PCR500
Powered PCR500 on
Loaded X1
Went to Preferences/MIDI/and checked the PCR stuff for Playback and Record
Went to Insert
Inserted Softsynth/SessionDrummer64
Loaded Program as talked about above
Made sure Input Echo was lit up Blue/On
Tested keys-Movement on screen and sound

Had slight delay cause of other plugs loaded-Hit the [FX] in the control bar,  No echo at all, sounds are as soon as you hit the keys.

Im assuming most of yours is good cause it will play the other synths so its gotta be something with the way the program is loading?   Just guessing

Ill check back later and see if you came up with anything yet  

Your in good company here with everyone else though,  Smart bunch of good peeps  

I was able to duplicate Losing the keys strokes but keep being able to mouse to get tones by powering off and on the keyboard.

I had to close all the way out of Sonar

Turn Power On to A-Pro

Launch Sonar

Bring your project back up 

Make sure you have input echo turned back on

And it fixed the lose of key strokes being able to trigger soft synths 

Thanks again for the additional replys! (Digi2ns) I have been busy and haven't had much time the last couple of days...I will be back at it this weekends and report back...thank you all very much!

Mornin' Frosty

Your welcome,

Ill check back as well to see if I can help at all if ya need me to verify something on mine

frosty,

here you go buddy,this should clear up some questions you have.

editing midi using a keyboard with SI Drums:
http://www.youtube.com/watch?v=k83UVo1OiKA

Also, drums usually have to be on MIDI channel 10.