It's a TOTAL guess, but I'm guessing that it's referring to missing Qt 4.x. I'm pretty sure the 5.9 series came stock with Qt 3.x, however Qt 4.x should be available via the repo. It should not be installed as an upgrade to 3, but rather alongside of 3.x. In other words, they should both be able to (and need to) coexist.
However, I've read your other post "killing me with the problems" and expect that a solution is probably not overly important for you. Sorry for the troubles you've been experiencing. It seems that your usage of the system is somehow different than most such that you're able to identify issues that may not have been observed before. It doesn't mean much to your situation at-hand but it would be great to get your feedback when VL 6 SOHO goes into beta or RC testing.