ORIGINAL: Charlie P.
What are you using to charge that higher capacity NiMH pack? If you're using the 50 mAh wall-wart that came with the Tx/Rx you probably have to leave it on a LOT longer, like 24 to 30 hours vs. 12 or 14 for the original pack.
Im usin an ace charger, i dialed it in at about 200 mah, yesthe original 45-50 mah wouldnt cut it