According the SNMPv2-MIB DEFINITIONS the right syntax should be "system.sysContact.0" and NOT "system.SysContact.0" as used in the above example 2251.
SNMPv2-MIB DEFINITIONS
...
sysContact OBJECT-TYPE
SYNTAX DisplayString (SIZE (0..255))
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"The textual identification of the contact person for this
managed node, together with information on how to contact
this person. If no contact information is known, the
value
is the zero-length string."
::= { system 4 }
