visa crashing

[falkpl]

I have an application running on LV8.6.1 and Visa 4.4 which uses 1 easysync usb to 4 port 232 and 2 usb to 2port 485 converters.  All works great until 25-30 minuts into execution where the program either freezes or closes out labview runtime engine with no error messages.  I have all error terminals wired through and am oprning a session in the start of the program and performing queries over these visa resources.  There is no memory leak (over 30 minutes memory usage climbs only from 62MB to 66MB) and there is 2 GB free.  I cant find any issue with the code and the device drivers (I wrote all eight device drivers) have been used in the past with no problems.  What could cause visa to close labview?  I know it is in the visa calls since when I run in simulation mode (visa calls bypassed and data is simulated) the application has run for over 24 hours before I stopped it.  Is this a hardware issue?  I asm stumpted and have never seen labview just quit with no error messages.

[MattBradley]

Can you run some of the instruments in simulation mode and others for real?  I would recommend simulating say, all of the 232 connections first and seeing if the problem remains.  Keep dividing the problem in half or so (and recognize that it might be more than one port!). 

[falkpl]

This is what I had the client do today,  I appears that it is either one of the pumps (232) or the mass flow meters (485) that is causing the crashes.  Very strange that the crashes are happening at a small time window 25-28 minutes after the code is run.  Is it possible that a buffer is built up on one of these devices and causing the communication to hang.  i would hope that visa would not crash out but would just throw out an exception.  I am making some progress though.