Intensive slider control use may lead to LabVIEW hang and system instability when coupled to event loop "Value Change"

Question

 Occasionally, over the past year or two, I have noticed on different machines and versions of LabVIEW (8.0 and 8.5) that intensive operation of the LabVIEW slider control (holding down the left mouse button and shaking the mouse quickly back and forth to move the slider for several seconds) may cause LabVIEW to hang with high CPU usage (50% on my current test machine, which has a Pentium IV "hyperthreaded" processor, so 50% is the max that a single thread can take up). In some instances, after the LabVIEW process is forced to quit, the system itself becomes unstable (more high CPU usage) or hangs, up to and including the need for a hard restart. I have seen this behavior both when handling slider change events the "old fashioned" way with a while loop and a case structure; and also when using a while loop with an event structure handling the "Value Change" event for the slider. 
Attached is an .rtf file dump of the front panel and block diagram of a simple test VI that replicates this problem in my hands (using an event structure). The loop count runs to at least several hundred iterations before the crash occurs.
At least for the "old fashioned" loop handling method, adding a forced wait of a few dozen msec per loop didn't seem to be a workaround. I haven't tried this idea with the event structure, but don't expect joy to follow. The possibility of a system hang discourages aggressive experimentation. 
Is this a known issue? Can anyone else replicate it (carefully)? In any case, I'd welcome other suggestions for workarounds.
Thanks,
Darin Nelson
Attachments:
Hang Slider.rtf ‏683 KB

Answer 1

Thanks for all your responses, and especially to those who are waggling their mice around trying to reproduce this. I'll respond to (most aspects of) the last several posts in one message.
LabViewGuruWannabe:
  I'll see if I can get the original code to post in a separate message, I posted the .rtf originally because I thought there might be filtering on forum posts (I'm sort of new here). But I doubt you re-created it wrong.
  The "more modern" test hardware was an Intel Core2 , 2.4 GHz, 2Gb RAM, on an Intel 965 family motherboard. As I said, it took me two tries to trigger the error on this hardware; in the case where it triggered, I was at almost 12000 iterations before things went south. 10000 iterations, therefore, might not be enough--or you might never get it, for all I know. My Pentium 4 Hyperthreaded machine (3.2 GHz, 2 Gb RAM) triggers the hang much more easily (always within 2500 iterations, usually within 1000), so there seems to be some hardware dependence here. Maybe the workaround is just to use hardware recent enough that no one not under the influence of strange compulsions will accidentally trigger the hang.
TonP:
  After reading your suggestion, I tried something even more radical  -- getting rid of the handling code altogether. I took the slider node out of the while loop, and removed all code inside the "Slide" case of the event structure.
 On my Pentium 4 machine, the hang triggered after 677 iterations.
Brian Beal:
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 Huh, I never even noticed that checkbox existed. Anyway, yes, I
kept the default to lock out the front panel while the event process. If I
disable it… I still get the hang.
Message Edited by dman on 02-04-2008 06:36 AM