I get that some time when I have to download, and I have to use putty to ssh and write some codes on it. But since I have term-vt100 installed thats what I use now. After writing it, it then works for a few days then it starts again. But I believe it occurs once u try to download a package that isn't 1.1.3 compatible. coz thats when mine starts to mess up. But anyway , this is what u shoud do, U can do just the first and see, or the next. I sometimes do both. Requires restarting your phone each time. I mean full restart. Do these using SSH
cd /Applications
chmod +s Installer.app/Installer
chown -R root:wheel Installer.app
or try this one
chmod 4755 /Applications/Installer.app/Installer
It should then work again.