I can't really help you on this one. It usually comes down to a laggy connection to the server in which, somehow, you've become desynchronized with it.
We really can't have a true synchronization with the client due to how PSOBB was coded. The server just keeps up it's state with the client and occasionally issues items, experience and what not.
Even SEGA had their own problems with this game:
http://forums.sega.com/showthread.php?118938-Disconnect-Error-and-Loss-of-Equipment (14 pages of error 100 and even loss of items. These are the people who posted on the forums, doesn't include those who actually followed the first post and sent an e-mail instead.)
You may be having MORE issues than you did in the past, but it's really all variable. Mostly, it comes down to how strong of a connection you have to the server and even what you're doing on the Internet at the time.
If you're saturating your connection, you're going to have a bad time.
If you have many hops to the server or lots of failed hops, you're going to have a bad time.
If your computer is lagging, you're going to have a bad time.
If you're playing on a wireless connection, even that comes into play. If you're far away from your router and have a poor connection to it, you're going to have a bad time.