Seriously Computerman, I've rooted an Ally 4 times now.
If it brings you back to the $, take out SD and try again.
Still $? Put SD in and try again.
Still? Take SD out.
Still? Put SD in.
Not working after 5-10 tries? Exit and restart adb shell.
SD in. SD out. SD in. SD out.
I would guess it has something to do with the phone's system trying to deal with the constantly changing file structure.
Sort of like when your kid asks: "Well... Can I not, not, not, not, not get a new toy?" and you're like... "Uhhh.....".