This usually means your OS and hard drive aren't getting along for whatever reason and they need to run a fsck (yes, that's the name of the command, it's short for "file system check") to get it all behaving again (whether they open up a remote KVM session and have you do this yourself or whether they themselves do that will depend on what level of support you're paying for, I guess). The hard drive wasn't performing up to what the OS "thought" it should do and went all panic-mode and locked everything down to try and minimize potential damage, basically.
This could be indicative of a number of things, but usually it means your hard drive probably isn't the most stable part of your system. That said, I had a dedicated box that'd throw this kind of error every six months or so that ended up lasting for four years before we decommissioned her this past summer. I wouldn't say it's anything the FTB server software itself precipitated, but it definitely could've been aggravated by it; Minecraft is rather I/O happy when it's running and a lot of the time the bottleneck will end up being how fast it can write to hard disk and read stuff up, and a number of mods only exacerbate this (I'm looking at you, Twilight Forest).
Verdict: See what your hosting company says about it, obviously, but definitely take backups of whatever may be vital on the server and if it survives this round and it happens again later, demand the company actually look at the hardware and ensure it isn't flaking out on you.
