Is this a front mount or 3pt blower (I didn't see it listed). If it's a front mount then you have more places that could be an issue. On my front mount Kubota snowblower there's a gear box that reduces the PTO speed and a second that has two output shafts (one for the fan and the other for the auger). Then you have the sub frame with the pto shaft that has a couple universal joints (I doubt they are your problem). I think I might remove both sheer bolts so only the gear box(s) are turning. That would eliminate the auger chain, the bearings on the auger, and ice on the auger/ fan. It would be an easy test. If I remember correctly the fill plug on my gearbox is also a breather. I would also check it for damage and look for some other way for water to get in. I would think that if you had a bad seal it would leak oil out of the gear box when in operation.
As for what others have said about warming up before using it, I would only do that as a very short term solution. If you do have enough water in your gearbox to cause it to freeze solid then you are at serious risk of doing damage. Freezing water could break the gearbox casing. Water will cause the metal to rust which will mix in with the water. Water alone is bad for bearings and gear surfaces, adding in rust will accelerate their wearing.