Some people are metabolically resistant by nature. A stall of 4-6 weeks isn't too uncommon even amongst those unfortunate Lowcarbers doing it completely by the book.

In your case, it seems you haven't been doing this WOE switch as it's supposed to be done (by experimenting with higher and lower calories - but I suspect you actually mean carbs, not calories?), not eating your ration of vegetables etc.

Just stick with the plan and realise this isn't a "quick fix", this is a way of life. You will get to your goal eventually if you're patient. If you surf around the board a bit and check old-timers here who've reached their goal weight (and stayed there), you'll notice that patience, being consequent and eating healthy really is the key to success.

Natrushka is an old-timer for instance. I don't know how much she visits the board nowadays, but her own site is here: http://www.geocities.com/gnattygrl/bflex.htm
She's very much into exercise.

Can't help you with the caliper thing, I'm afraid. I only use http://mybodycomp.com to track my progress.

Best of luck!