On a Redhat Linux 4.3 32bit machine, we just installed oracle client 10.2.0.1.
While we were trying to use sqlplus as below, it hanged:
$ sqlplus /nolog
Not only this command all the commands with "sqlplus" were also hanged.
But tnsping was working fine.
This is a bug [MOS Note ID 338461.1].
When the machine uptime hits 248 days, this bug hits.
In our case up time was 406 days.
And there are two solution restart the machine or apply patch 4612267.
In our case we applied the patch and just after patch installation, "sqlplus" started working fine.