I am guessing your on a PS3 Phat right ?
If so i had same issue ,should not keep doing this as long as you update MultiMAN & install new update. I had it happen also but i restarted & updated MM. Installed update ,everything is ok. It might be just a first run or that we had multiMAN for 421 maybe just a hunch ,it remembered 421 & is a small Glitch.I am not sure, but the update solved my issue & i did not give it a chance to try a second time ,being i installed the update before i gave it another shot..
Paine & simple either update to MultiMAN ver 04.07.05 i believe that was the new update.
Or do it the way i did .
Downgrade back to REX 355.3 first.
How i Downgrade my PS3 every time before installing a new CFW.
First make sure your PS3 is QA Flagged
Simple way ,no need for 999 Downgrade PUP.
Examples = Unless you downgraded your PS3 via Flasher, or QA Flag is not set.
Either way this does not require a 999 Downgrade..
Starting from REX 421.1 QA Flagged PS3
"Set to these settings Below"
Last option CEX/QA
Bottom Network Settings
XMB SET QA Flag with Button Combo
= Enable QA "3 Icons"
Go in debug settings- System Update Debug
Downgrade to REX 355.3 Through XMB
Once downgraded to REX 355.3
ToolBox Open Again
Network - ICON
Do button Combo
= Set QA Flag "3 Icons" Again
Update direct through XMB To Rebug 430.1
Simple & safe way to downgrade & update.
I have downgrade/update like this more than 20x on 2 PS3s.
Downgrading this way = Never need => 999 Downgrade PUP.
This method can be used to Up/Downgrade from Rebug 430 also, same way using REX 355.3/4..
This is on a NON downgraded PS3 = Never seen a Flasher
You can do this same way with a Downgraded PS3 but remember to Run Toggle QA pkg from XMB till you hear 3 beeps & confirm Button Combo to Dehash Syscon after downgrade to be safe..
I though this will help some of you guys ,to understand Up/Downgrading .
I was going to make a simple TUT since i have done this so many times.
This has been "Flawless" for me on more then 3 PS3s.
People worry to much ,Rebug 430.1 works just as great as REX 421.1.
No issue except a small hiccup when Setting game/Quitting MultiMAN first run..
QA Flag your PS3 & Up/Downgrade, is good practice,get to know your PS3 .
When you have to downgrade/Update your heart will not skip a beat.
I am very Calm when i Update/Downgrade now unlike before QA Flag