I have yet to submit my ticket on this, but I am wondering if we can put heads together in this thread and find a common factor on the technical side of our systems.  Even after 4 pages I have noticed no one has mentioned anything about their systems.

I get the CTD when entering constraints.  That's the only spot I get the CTD so far.  In order to help Captain Sim see if there is a common componant causing this, I should mention:

• OS - Windows Vista Ultimate x64
  
• GPU - 4x ATI Radeon HD 4870 X2 Dual Core/2GB Memory
  
• CPU - AMD Athlon X2 6400+ 3.2GHz Dual Core
  
• Memory: 8GB OCZ DDR2
  

Really those are the only 4 things that could possibly affect anything in FSX, so I won't go any further than that.  I'll also include this information when I submit my ticket to CS  :)

On my particular system, I can do many successful flights as long as I do not try to enter or modify an altitude/speed constraint manually.