1. Verify that the new install source actually still exists and contains a "repodata" subdirectory as needed by yast.
2. Clean the cache with the command 'rug cc'.
3. Restart the ZMD daemon with the command 'rug restart'.
4. Try adding the new source at the command line. Example:
'rug sa --type=zypp
ftp://full.url.to/your/repo/' this-repo-name'
(replace 'this-repo-name' with something meaningful, like 'ftp-install' or 'mike-rpms' or whatever)