Help Icons invisible after an Install

Have posted this in aother section but no replys as yet. So thought I would try here.

I have a 1.1.2 OTB jail broken iphone on O2 contract (UK)
over the past month or so I have been happily installing and un-installing apps with installer,
over the past week or 2 though I have noticed that after I install an app and the iphone goes to the Slide to open screen, when my dock comes back on 3 icons are invisible, there is an empty space where they should be, if i dbl tap the empty space the reappear. namely Safari which i have on the bottom dock, Itunes and You Tube which are on my second screen.. I have moved them about, used customize to make them visible, but they still vanish,
if i put the iphone into sleep or shut down they are fine, they only vanish after an install or un-install..
any help would be appreciated, this is more of an annoyance than a problem
I would just like some help if anyone has a solution, as its cracking me up lol

Thanks in advance.