Help Memory not updating kinda problem :S

[Mystic]

I messed up the title and it won't let me edit it :S .... anyway:

My problem is not the fact that my memory is low but every time I try to install an app my phone says the memory is full although I have much more memory then the app needs :S

I rebooted the phone and everything but still if the app is bigger then 8 mb it won't install although I have like 40 mb memory left , any suggestions ?:S