My ride to work this morning took a bit longer than usual because my Alfine hub appears to be stuck in 4th gear, so I was spinning out at 16/17mph. I'm not sure if this is due to the overnight temperature of -5C freezing up my gubbins or a mechanical defect somewhere in the setup. I can actuate the shifter so that the gear indicator moves through gears 5, 6 ,7, 8 and back to 4th but there's no corresponding change of gear within the hub. I can't move the shifter below 4th gear, the thumb shifter remains solid. I can move the pulley down at the hub with my thumb so I think the problem must be somewhere outwith the hub itself. I've only had time for a quick look while I put it in the office bike shed and will take another look at lunchtime. Has this happened to anyone else or does anyone have any suggestions as to the reason for this? I've just remembered: over the last few commutes I've noticed what felt like a bit of slack in the cable when shifting down gears. The initial thumb stroke gave no resistance and no change of gear until the second thumb stroke when it all felt normal again. Has something maybe come adrift inside the shifter?