A while ago I documented how to connect the DB2 Client to a remote database, which is useful if you want to run the DB2 client on your local machine and connect to various DB2 servers.  Recently I came across this error trying to add a database  using the DB2 Configuration Assistant.
CCA3054N The ODBC DSN could not be registered
After checking and re-checking my Database configuration and deciding I had all the information correct I started searching and found the anwer
The error is caused by the Microsoft UAC (User Account Control) feature included in Windows Vista, 7, and 2008. In order to create a system DSN, local administrative privileges are required. Even if the logon user is a local administrator, the UAC feature causes the logon user to only include the standard user token. As a result, Configuration Assistant will not be able to detect the administrative authority and the process of trying to add the system DSN will fail.
I quit the Configuration Assistant, ran it again using “Run as Administrator” and magically it worked.