I am experiencing the same behaviour with my T665C. Normally the top end of my battery is 4.28.
It has seemed to me that it recently was not charging to 100% before the orange light would go out. Upon turning on the unit, it would display a variable charge above 4.00 but not the full 4.28. I thought the battery was getting old. I keep mine charged quite frequently so the battery seldom gets below 80%.
Anyhow, I was having problems with the KB11 working and had to turn off a specific program (which keeps the infra-red beaming function turned to off) and it seemed that the charging behaviour seemed to improve, or at least it more frequently reads 4.28 again after a charge.
Its good to hear that this may be just a slow reporting issue and not an actual battery-aging issue.
Is there any suggestions people may have on how to improve the battery reporting (I use popclock to gain quick info on the battery, but seldom for the time heh heh) on such a unit. Also, any comments on battery hygiene and how to extend "battery-time" (eg. turn off IR beaming, dim the screen with dimmer, don't play too much music, turn off unit sounds) on such a unit are much welcomed.