We are currently using the initial release of the FtB Mod Pack due to the removal of the Extra Bees mod in the updates. In discussion with people who have knowledge of servers, it has become clear to me that corruption can result from updating due to the removal of mods which were already in use. That being said, we are going to wait until the 1.4.5 Full Release update or when the next Extra Bees addition occurs to prevent any issues.
If anyone is having problems due to having already upgraded then this link that a kind viewer provided should fix it:
FtB Downgrade Fix