When testing on CMUCL (cmu-snapshot-2013-04__20d_unicode_-linux-x86)
every system fails with this error:
Error in function KERNEL:CLASS-TYPEP:
Class is currently invalid: #<KERNEL::STANDARD-CLASS ASDF/SYSTEM:SYSTEM
{585CFA1D}>
[Condition of type SIMPLE-ERROR]
Looks like an ASDF upgrade problem.