CRM 4.0 Login failes 'key expired'

On our CRM 4.0 Dev environment we experienced the following behaviour:
When opening CRM this message appeared:

The key specified to compute a hash value is expired, only active keys are valid.  Expired Key : CrmKey...

After searching on the machine I found that the Async service did not run, I started it and this solved the issue.

Henry Cordes
My thoughts exactly...