oracle.exe error

I am trying to configure dead connection cetection by setting
SQLNET.EXPIRE_TIME=10 in sqlnet.ora file
But after database is started I get an fatal Oracle.exe error and the instance and service are shutted down.
Could you guys tell me what's wrong with this parameter?
Thanx

Purposeof sqlnet.expire_time parameter is to "Determines time interval to send a probe to verify the session is alive".

Default: None

Minimum Value: 0 minutes

Recommended Value: 10 minutes

Example: sqlnet.expire_time=10
===========================
You are not going to get information from using this parameter in sqlnet.ora file. Best is to turn the tracing on at support level and start database. Please check Oracle alert log and listener.log file before you proceed with more investigation.

I hope this helps.

Cheers!!!