Hi,
I have not seen this, it only happens on some machines, but I have had other customers report this bug.
There is actually a 1.5.6 version on the web site now (it has only been there a few days). The only difference between 1.5.5 and 1.5.6 is that the redraw routines have been changed to overcome a more serious redraw bug, but it should also fix this one.
Please let me know.
Don