I am sometimes getting this error when mousing over the icon for Fubar_WeaponRebuffFu:
Error: attempt to concatenate field 'VERSION' (a nil value)
[EDIT] I found the problem. It seems that WeaponRebuff now comes with its own internal Fubar plugin (it had been a separate addon previously IIRC). I noticed the second icon earlier this evening. Using that one caused me no issues. My apologies for the confusion and/or inconvenience.