Hello everyone, 
Basically i have 2 VIs, one running on a PXI, lets call it PXI.vi and one on the pc, GUI.vi 
I started testing my application some days ago and after 3 hours of running i got the error in the picture. 
Error -1073807339 occured at VISA Write in PXI.vi 
Reason: Timeout expired before operation completed. 
Then immediately also this error: 
Unable to locate variable in the shared variable engine. Deployment of the variable may have failed. 
I restarted the PXI and started the test and it happened again after 2 hours. 
The third time even sooner. 
It is always 2 variables that cause this problem.They are used to pass information about error happening on a instrument. 
So actually they are not even used when giving the message. 
I check them in a loop every second. 
They are not buffered. I initialize them when the vi starts 
I am using Labview 2011 and windows 7 
Thank ou in advance for your time.