exploding memory...

Hi,

I have an Iphone 3G, I recently installed Navigon GPS which is supposed to use 1,4 GO on the iphone.

when I display the file on my computer, the size is correct, but when I plug back my IPhone on Itune and check the Applic. memory use, it says that applications are using a total of 3,5 GO !!

on the windows browser my "Mobile Applications" folder size is 1,53 GO, I am totally confused, it is including all the applications downloaded that I am not even installing on the Iphone ...

Any Ideas on this Memory blast ??