On March 20, 2004, approximately 1430 mountain standard time, a Bellanca 7GCBC, N90076, registered to and being operated/flown by a commercial pilot sustained substantial damage during a loss of control on landing and subsequent nose over event at a private landing site approximately one nautical mile east-southeast of Marion, Montana. The pilot was uninjured. Visual meteorological conditions existed and no flight plan had been filed. The flight, which was personal, was operated under 14 CFR 91 and originated from Bonners Ferry, Idaho, earlier in the day. The pilot reported to a Federal Aviation Administration inspector that he was returning from breakfast at Bonners Ferry and was landing on runway 20 at the newly established landing site. During the landing the pilot encountered a strong gust of wind from the right and the aircraft veered off the runway, hit a snow bank and nosed over. The pilot subsequently reported (see attached NTSB Form 6120.1/2) that he noted the windsock indicating calm winds upon landing and that on touchdown the aircraft "...started to the left...." He applied right rudder and the aircraft veered right. With full left rudder the aircraft departed the runway impacting a snowbank and then nosing over. The pilot reported that another aircraft circling the landing site at the time informed "...me that a gust of wind came up from my right rear...." The Cabin Creek Landing site is a development of homes situated around a paved runway of unknown length (refer to Chart I and Attachment A-I). The landing site had not received airspace authorization from the Federal Aviation Administration at the time of the accident and therefore, had no assigned identifier.