I have seen many threads on this, and yes I have researched before coming here.

I have iPhone 3GS 8GB Firmware - 4.3.5

I have done the jailbreak then booted in tethered afterwards and it works, soon as I install untethered again it does not open and has a blank icon.

Any idea's guys?

This is behavior by design. Unless you have the first release of the 3GS with the old bootloader, you do not have an untethered jailbreak for iOS 4.3.5. There is no untethered jailbreak for the new bootrom 3GS or 4. The only untethered 4.3.5 is for the 3G (and you don't want to run 4.3.5 on a 3G anyways, it's terrible).

If you have an SHSH on file for 4.3.3, you should downgrade to 4.3.3 and jailbreak -- it's untethered.