Labview 8.0 - My main vi has started to hang!

Question

Hello,
I have written some code in LabView 8.0 which consists of a main VI and several sub-VIs.  The code controls a DAQMx DI-6221 board doing some basic digital I/O.
I haven't made any changes to the main VI code for a number of days.  Gradually over the last few days the VI has started behaving oddly (ie. showing some of the front panel with a portion which is frozen).  This happened more and more each time I have opened the VI.  Today, when I try and load it the VI just hangs at the LabView splash screen.  I can load any of the subVIs which the main VI uses with no problems whatsoever.  The computer is not connected to a network and does not have a virus (I checked today).
Anyone able to help with ideas?!  I'm quite desperate but I don't want to resort to reinstallation of LabView just yet.  The fault really did seem to come on slowly getting worse every time the VI was opened.  Sometimes the front panel does appear but it can't be run and I just get the 'paint' effect where you can drag the window around the screen creating lots of outlines of the window.
Cheers,
Rob

Answer 1

Hello Ibbo,
Corrupt VIs do not occur often, however, they do occur. I have been able to open your main VI in LabVIEW 2010 and then save it for a version 8.0 for yourself.  You should find it attached.  It should still be able to load your SubVIs and run when your click the 'Run' arrow. 
If you notice that the performance of a VI is degrading, and you believe it is corrupted, a quick trick that has known to work in the past, but not guaranteed, is:
Open a Blank VI
Open the Existing VI's Block Diagram
Press Ctrl+A to select the entire Block Diagram
Press Ctrl+C to copy all of the code
In the Blank VI's block diagram, press Ctrl+V to paste the code.
Save the new VI with a new, different name.
If the new VI still appears sluggish after the paste, press Ctrl+Shift+Run Button Click to recompile the code in the background.
Corrupt VIs can occur more often when using a newer Operating System with an older, unsupported version of LabVIEW, such as LabVIEW 8 on Windows 7.  Which OS do you have?
Looking at the code, I have also noticed that you have a While Loop in another While Loop.  Generally speaking, when you believe you require such function, or many Nested Case Structures, that VI is generally a good candidate for a State Machine architecture. 
I would also like to promote the comments that the users above have made about changes that can improve the code and make it more maintainable for the future.
Regards,
George T.
Applications Engineering Specialist
National Instruments UK and Ireland
Attachments:
UKsupport_DIGITAL%20CONTROL%20v4[1].vi ‏84 KB