It appears that, according to proposed IRS regulations, a partner who holds both kinds of interests in an LLC must be considered a general partner, and not a limited partner:
"However, if an individual holds two types of interests in the entity classified as a partnership, and one of the interests is not treated as a limited partnership interest (e.g., a state-law general partnership interest), the individual would not be treated as holding a limited partnership interest (Prop. Regs. Sec. 1.469-5(e)(3)(ii))." - See more at: http://www.thetaxadviser.com/issues/2012/jun/clinic-story-04.html#sthash.q2G8Pvqt.dpuf
