When setting the Messaging Gateway (SMG) Liveupdate configuration, the username and password fields are not checked for invalid characters which may cause issues when attempting to authenticate to either the proxy server or the local Liveupdate Administrator (LUA) host.
This issue has been addressed with the SMG 10.7.5 release.
Following the update to SMG 10.7.5 the only character which is disallowed in the LiveUpdate username or password is the / character
Workaround for SMG 10.7.4 and earlier
Please visually confirm that the username field does not contain any of the following characters: /, @, % or whitespace