dubiously

from WordNet (r) 3.0 (2006)

dubiously
    adv 1: in a questionable and dubious manner; "these were estates
           his father questionably acquired" [syn: {questionably},
           {dubiously}]
    2: in a doubtful manner; "Gerald shook his head doubtfully"
       [syn: {doubtfully}, {dubiously}]

from The Collaborative International Dictionary of English v.0.48

Dubiously \Du"bi*ous*ly\, adv.
   In a dubious manner.
   [1913 Webster]