Sounds like you have data corruption. When you say "network drive", that's a red flag right there. It's very hard to configure NFS to get data reliability with PostgreSQL. It's AFAIK impossible to configure SMB to get it. So most likely, you got data corruption in the crash, because the network mount was not safe.
2662 is the oid index on pg_class - which is basically the index on the table that lists which tables and indexes exist in your database. When this is corrupt, well, you're in serious trouble.
Your best bet at this point is trying to start a standalone backend (with the main one shut down of course) with "-P" which turns off usage of system indexes. Then attempt to REINDEX pg_class, and possibly the rest of the system indexes. If this worked, do a pg_dump backup right away, and re-initialize the database. There is likely more corruption in the system.
If this does not work, try posting to the pgsql-general mailinglist, you're likely to get more and quicker responses there. But most likely, it's back to your backups - or hire a data recovery expert if your data is really important and you don't have working backups.