Packed.Cupx!gen3 is a heuristic detection for files that may have been obfuscated or encrypted in order to conceal them from antivirus software.
This heuristic detection is used to detect threats associated with multiple threat families.
Virus definitions dated March 31, 2010 or earlier detect this threat as Packed.Generic.272.
For more information, please see the following resource:
Click for a more detailed description of Rapid Release and Daily Certified virus definitions.