OS X Mavericks can't be verified!

I'm using late 2009 MacBook Pro with Mac OS X Snow Leopard 10.6.8

I was trying to download the OS X Mavericks this morning and it's done.

but, when I was trying to install the OS, this keep happening :

the file was not corrupted, the size is 5.31 Gb.

I've already run disk utility to verify my HDD, and it was ok.

all of my software also up to date.

how to solved this problem? please help!

*sorry for my english