Just wondering....if it were a clutch release problem, I would think that there would be some tactile hint. IE, you would probably feel less throw, and might even notice the drag on the disc at stop....the car would want to continue forward despite the pedal being pushed all the way in.
If you don't have much of a tactile sensation...
1. does "pumping" the clutch help?
2. have you checked to see if your fluid level is low, or if there is evidence of a fluid leak (esp out the bottom of the bellhousing (assuming in internal TO bearing))?
I just wonder about the clutch issue, as anytime I've had problems with my hydraulic TO, it didn't matter what gear I was in or trying to go to, it just didn't want to engage.
That said, I'd wonder about the (cable ?) shifter setup...loose or out of adjustment. Put your hands on the mechinism as see if it seems loose at all. If you're truely having problems with a particular exchange, I would think shift mechinism first, trany second. As I've said, in my experience, clutch problems usually manifest in all gears.
My $0.02, and not worth that much.