If you are on Caché 2008.2 or higher, there is another license decoding utility:

do DiagnoseKey^%SYS.LICENSE

This will decode the active license key just like $System.License.Decode(), but it also looks at the current system and compares it with the license key.  It will list out any problems it finds with the key and is pretty good at catching most of the common issues already discussed.  The results are also a good summary to give support or a sales representative if you need to report a license related problem.

If you want to use this on a non-active license key, this tool can be pointed at a particular cache.key file with the syntax:

do DiagnoseKey^%SYS.LICENSE("<FullPathAndKeyFileName>")