Can't select ISO file to install GuestOS

[hachucat2]

Sorry poor english!!!!!
My language is Trad Chinese

Actually. I have asked this question once, but no conclusion
viewtopic.php?f=6&t=66783


about this problem in this video
http://youtu.be/Tlr-kxnNtKs



They said this problem not "BUG"
OK, but it really troubled me and i have no idea how to solve it.
If reinstall OS, maybe can solve.
but this problem repeat happen chance is very high.

i hope someone know how to help me to solve this.