Oracle server 11g stops working with 12541 error until IP address changes

Running Oracle 11g 11.2.0.1.0

Server mysteriously stopped accepting connections to its databases. In other words, you run sqlplus and try connecting as any account and get an error that the listener could not be found.

The sqlnet.log kept giving the error:

Fatal NI connect error 12541, connecting to:

(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=MYDBSERVER)(PORT=1521))(CONNECT_DATA=(SID=MYDB)(CID=(PROGRAM=C:\app\administrator\product\11.2.0\dbhome_1\bin\emagent.exe)(HOST=MYDBSERVER)(USER=SYSTEM))))

VERSION INFORMATION:
TNS for 32-bit Windows: Version 11.2.0.1.0 - Production
Windows NT TCP/IP NT Protocol Adapter for 32-bit Windows: Version 11.2.0.1.0 - Production
Time: 1-DEC-2014 17:27:57
Tracing not turned on.
Tns error struct:
ns main err code: 12541
TNS-12541: TNS:no listener
ns secondary err code: 12560
nt main err code: 511
TNS-00511: No listener
nt secondary err code: 61
nt OS err code: 0

Tried restarting multiple times. Tried stopping starting the listener and database service.

The database wasn't accessible until I changed the IP address. Any ideas as to how this could happen? Checked the windows event logs but nothing really jumps out except the machine having to reboot to do windows updates. Could the oracle database server configuration or related files get corrupted from a restart?

Below is the config files.

Here is the listener file:

SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
  (SID_NAME = Mydb)
  (ORACLE_HOME = C:\app\administrator\product\11.2.0\dbhome_1)
  (PROGRAM = extproc)
  (ENVS = "EXTPROC_DLLS=ONLY:C:\app\administrator\product\11.2.0\dbhome_1\bin\oraclr11.dll")
  )
)

LISTENER =
(DESCRIPTION =

(ADDRESS = (PROTOCOL = TCP)(HOST = MYDBSERVER)(PORT = 1521))
 )

ADR_BASE_LISTENER = C:\app\administrator

tnsnames file:

Mydb=
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = MYDBSERVER)(PORT = 1521))
(CONNECT_DATA =
  (SERVER = DEDICATED)
  (SERVICE_NAME = Mydb)
)
)