Can't connect: Mod rejection

[Adatrem]

I've just downloaded Resonant Rise Version 4.3.0.0-b without changing/deactivating any mod and can't connect to the server. The error is:
Mod rejections [FMLMod:BiomesOPlenty{5.0.0.2162}
After downloading the proper BiomesOplenty Version from the internet and putting it into my mods folder I got some weird forge mod loader error when I tried to connect to the server (If you wonder YES I deleted the old BiomesOPlenty before putting the other version in).
What am I doing wrong?

 

[TheAloneOne]

Try reinstalling the pack

 

[Adatrem]

Reinstalled the Pack; still got same problem. A Friend of mine installed the pack too and got the same error
EDIT: Just added the proper Version of BiomesOPlenty through the ATLauncher and deactivated the newer BiOP; Error when connecting to the server is:
Internal Exception: java.lang.ClassCastException:
net.minecraftforge.fml.common.network.handshake.FMLHandshakeMessage$HandshakeAck cannot be cast to
net.minecraftforge.fml.common.network.handshake.FMLHandshakeMessage$RegistryData

 

[daria530]

I am also having this issue and I have reinstalled this modpack 3 times

 

[TheAloneOne]

Hmm, interesting.

 

[Phyl_Swyft]

It's fixed.