Cisco WAN :: Installing New CF In 3845 Router?

I am installing Cisco blank CF upgrades (double the capacity of the CF that came with the router) in Cisco 3845 routers and I cannot get the IOS to load.
 
Network security requires tftp be disabled, so I am limited to xmodem.  Slow, but it works. I know the IOS download is good, because I can load it on the CF that came with the router.
 
I can install, format and read the new flash.  But the download locks up and bombs about 1/3 of the way through.
 
Note:  CF that came with the router was "C" so I used the format flash: command.  The new flash reads the same as the old, except that there is no file IOS loaded.
 
I've never had an issue upgrading an IOS, but this is my first shot at installing on a new CF.