Class Server

gmod: "server uses different class tables"?

ok i bought gmod 10 through steam. its worked fine for about a month, but all of the sudden when i try to join a multiplayer game it says "disconnectede: server uses different class tables" this is annoying and i can get rid of it. it happened right after i tried using the advanced duplicator for the 1st time. i coppied a prop, messed around with spawning it, and when i tried taking the prop to a multiplayer server, i coundt join any servers. it is continueing now even though i have restarte4d my computer several times and deleted all of my saved things in the advanced duplicator tool. also, singleplayer works just fine.
anybody know how i can help? i get a sense after googling it that its been a infamous problem.

i get the same thing after an update, it usually means that:

A) the server is either ahead of you on updates, and you need to update your copy of gmod (it does a check for updates automatically when you start gmod).
B)the server is behind you on updates, and you need to wait a bit (a day or two) for the server to realize this and update.

there is a new update out today (july 14th), so i take the time to update now.

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