Ok, not really sure what just happened but I wanted to see if my derailleur had any more movement left in it going towards the big ring. I shifted it into position and then pushed outward with my hand on the cage. It sort of clicked and moved over a little bit more. Lo and behold, the bike now shifts onto the big ring even when on the small gears in back. Seems to me like some dirt must have gotten in there and jammed things up (I thought I kept it reasonably clean but I guess not good enough). I'll know tomorrow morning if my "fix" worked but for now it seems to have. Thanks!