I have solved the problem! See the original post, "A strange problem with modeless dialog boxes", for details.
This is a repost, incorporating the latest simplifications of the problem statement, and a minimal reproducible example of the code...
I'm having a problem with modeless dialog boxes...
application
c++
debugging
dialog box
document scanning
event handling
graphics
gui
linked list
modeless
multithreading
performance
progress bar
sleep function
software optimization
systemcalls
timer
user interface
window procedure
windows development
The statvfs() call in SUA may fail with the following error on a Windows 7 or Windows Server 2008 R2 based system: statvfs(): errno = 88 (Value too large to be stored in data type)
Link Removed
When I rebooted my computer this AM a number of icons on the desktop had been replaced with the windows default icon used when Windows can't find the icon specified.
Also, I could not access a number of root folders and the programs in them would not run from system calls as in the startup...