I think every SE-R post I've seen here, the owner has been from SoCal - so I might be shooting in the dark. Maybe I'll get one of the Nissan techs to help me out.
When ever the temp is below 30'ish - 2nd gear grinds. I read of this issue on the Z early on but has been fixed with a different trans

It isn't bad - but it is clear it is only when it's cold. The colder it is the longer it lasts.
I'd rather not take it in for a replacement - unless of course it is a known issue. Has anyone tried running synthetic manual trans fluid? Does this help? I guess I'd rather do that than have the trans replaced.
Background - '06 SE-R, 6-speed about 2K miles. It has done it since new'ish. It is generally parked in a garage so it doesn't happen all that often.