Hi,
I agree with Jamie that it would be good to upgrade, it is a very old version, but that is not what I would do to solve this problem and doing that might actually complicate it depending on what the real problem is.
First thing to do is Basic Troubleshooting, clear the mojoportal log, try to save the large table, then see if any error is logged.
Were you able to edit this large content previously and the problem just started?
Also I'm not even clear on what problem you are having, please clarify what you mean by:
I am able to manually drop it in to the database and it displays fine.
You are editing mojoPortal tables directly in SQL Server and it works?
I would check that the database and/or the site is not running out of disk space or any other errors that the database might be logging in addition to any clues the mojoPortal log.
Maybe if there are clues in the log we can suggest further steps.
Hope it helps,
Joe
Before you consider upgrading find out what version of MS SQL you have, if it is SQL 2005/2008 you can upgrade to the latest version but if SQL 2000 you cannot upgrade all the way to the latest version without migrating to a supported version of SQL Server.