Cisco's response to this issue is posted in the Release note of CSCtg55418. Please note that this issue is not a hardware, software, or manufacturing defect.
Text from the Release-note:
Since the release of Cisco ASA software version 8.3(1) and the related recommendation
to upgrade the RAM in all Cisco ASA-5520s and/or ASA-5540s, some Cisco ASA customers
have contacted the TAC reporting devices with only one DIMM socket.
Working with these customers, Cisco conducted a detailed investigation and identified the
affected devices as Cisco ASA-5510s that were modified post-manufacture to look like
Cisco ASA-5520s or Cisco ASA-5540s. Cisco has always manufactured these products
with either 4 or 2 DIMM sockets, so these modifications were completed without our consent and
outside of our control. Cisco takes this situation very seriously and through our
Brand Protection team is sharing these findings with the appropriate authorities.
Cisco's commitment will always be to quality products and supporting our customers.
That is why we also offer service and support contracts for products purchased from authorized Cisco partners.
If your device was purchased from an authorized Cisco partner, it will be supported.
In other cases we encourage you to contact the original point of purchase to determine next steps.
