Trying to upgrade 3640 IOS from IP (c3640-i-mz.122-5d) to IP Plus. Router has 32mb memory, a 1FE2W network mod and a WIC-1DSU-T1 card. Release notes say I have enough memory, however when I upgraded via tftp with c3640-is-mz.121-5 or c3640-is-mz.120-13 and do a show interfaces, there are no interfaces displayed and of course there are no interfaces for me to configure. Any suggestions would be greatly appreciated. Thank you.