Hi David,
Description is the main field, it stores the body of the blog post. The field is ntext data type so I think it should hold up to 1GB of data unless your server is configured with a limit somehow or maybe its lower in sql 2000 vs 2005/2008.
Meta Keywords and meta description are limited to 255 chars.
Is the content of this post extremely long?
I've not encountered this error.
Hope it helps,
Joe