I have jailbroken many, many phones with much success, but I can't do my brother's 4 with 4.3.2. It gets stuck when it's installing ramdisk and never goes through.
I am assuming your using windows.
Right click redsnow icon, click properties, click compatibility tab. Select Run this program in compatibility for: click Windows XP. (i selected windows vista, but more people prefer windows XP)
Then select run as administrator.
Re-jailbreak and it should be fine.