actually i just found a thread in this forum just like yours--
and im quoting user c3shooter "Suggest you contact marlin- (marlingun.com) and see if they have a manual. Common problems to rimfires are: Action is cruddy and needs cleaning (22 RF ammo is pretty dirty) OR: Gun has been dry fired too much, and pin has put a burr on mouth of chamber (sign is a scratch mark on side of case when extracting) IF that is the problem, DO NOT REMOVE THE BURR- but I can tell you how to fix it- easily."
http://www.firearmstalk.com/forums/f37/marlin-model-99m1-9102/#post56136
no after action report was filed by the original poster, so i do not know what he did...