SubVI not executable error only when opening another VI in same instance of LabView

Question

I have a VI (ill refer to as "A")that I have written for some of my components of my system, one of them being a loop that polls a pump controller to pick up the data (pressure, volume, etc.) coming from the pump.  Now I have been able to get a VI (Ill refer to as "B")from that manufacturer that allows me to not only get the data, but write a command to my pump controller to control my pumps from labview.  So, my goal was to just open both VI's (A and B), "copy and paste" (from B to A)so to speak, so that I could have controls incorporated into my existing VI (A) that has the controls for the rest of my components.  However, when i open both VIs in the same instance of labview, i always get errors from the second VI that i open.  Keep in mind that when running just one VI in an instance of labview, it gives me no errors.  The furthest ive gotten was to open my "B" VI first, then open my "A" VI, in which the "A" VI only gives me "not an executable error"  After investigating the source of the error, it says that it's coming from the loop inside my "A" VI of which polls my pump controller to get the data.  So basically what im thinking is that the programming thinks that one VI is coming up with the data, and one is controlling it, so it gets confused as to whats actually going on. 
Any help or suggestions would be greatly appreciated.  I can attach some of the VIs if need, figured Id try to get some ideas first as to maybe what is going on...
Thanks in advance!
Matt

Answer 1

What errors?  Do they have an error number?  Do they have a description?
Since you said communication, I'm going to assume that it is serial communication and is using VISA drivers.
It is very likely the two VI's are stepping on each other's communication while they are trying to communicate with the pump.
Why don't you post the two VI's so we can see what you are doing?