Hi,
 
The strangest thing happened today. I opened a previous project (mixture of live instruments and VST's), and decided to try inserting a Session Drummer instance using the "MIDI Source and All Synth Outputs" option in the soft synth options. It plays the original drum track great, however there is now a latency issue for all the other VST's including Session Drummer. It all plays back fine, but there's a serious delay if you want to record anything. My latency settings are ideal, and it ONLY happens in this particular project. Is there some sort of funky thing that I'm missing?

Have you used perfect space or any other convolution reverbs?
 
Have you used LP-64 EQ or LP-64 Multiband?
 
Have you used the PC Concrete Limiter or other look ahead FX?

On that particular project, look for other sound enhancing plug-ins, some of them cause considerable latency, whenever I use perfect space, I turn that off, exit & save.

Also on your tool bar, the tools that show mute, there is a PDC radio button, enable that will take care of latency as well.

jb101 & Rski......you guys ROCK.

Turning off the LP-64 EQ and LP-64 Multiband totally fixed the problem. THANK YOU.

Any idea why that problem exists in the first place?

Those plugins fall in a class of effects that require a look-ahead buffer to work properly. That buffer means that everything must be delayed a bit in order to stay in sync.

Some plug-ins take a lot of processing power, and others need to "look ahead" so they can react "before" the event.
 
When tracking,I tend to use Lexicon Pantheon or Breverb, and then replace them with Convolution Reverb if I want.  I will turn off the PC Concrete Limiter if I'm tracking.
 
Things like LP-64 i will only use on mixdown, or disable on tracking.
 
Glad you got it sorted.