I have set up a Big Dig server, which runs on Minecraft 1.5.2, using the Spigot/Forge combination MCPC, which I got from Yive's Mirror.
Plugins like MCMMO and Worldedit seem to be working fine, but when I execute a command from Essentials I get the error:
"An internal error occurred while attempting to perform this command"
I have checked to make sure no plugins have gotten into the mods or coremods folders.
None of my plugins were working at all until I changed "custom-class-loader" to false in mcpc.yml
I have included a log of my server where I try to execute an essentials command, copied with Notepad++
http://pastebin.com/UB9SRFt0