The localization for "Mining" is missing in the file BTS-Mini.lua. According to wowhead this should beL["Mining"] = GetSpellInfo(32606)
One of my guild mates posted his mining list, which broke the GuildCraft browser for him and the rest of the guild. I looked into the source code and it seems that a lot of professions are missing, like skinning and herbalism.
Removing line 24 from BTS-Mini.lua works fine as a workaround, but it would be great if you could the fix the cause of this problem.
Great addon otherwise!