i am having a lot of trouble getting this to work

when i issue the command

sed -i ‘s/udpcastsrc=“…/packages/udpcast-20071228.tar.gz”/udpcastsrc=“…/packages/udpcast-20120424.tar.gz”/’ …/lib/common/config.sh

i get

sed: -e expression #1, char 27: unknown option to `s’

can someone tell me what i am doing wrong

i am using ubuntu 13.10