hum.
can you tell me if your 900c is an original 900c or an upgraded 900?
which battery did you change, main battery or backup?
if it was the main battery, your internal battery switch may be broken. not sure... mine is broken yet my 900 doesn't hard reset if i change the battery when the unit is powered off.
(if it is powered on, then yeah it will hard reset
)
if it was the backup battery... well, that's mysterious... i guess just another glitch of the 900's flaky power system.
oh or was it just the main battery fully discharged when the 900c wouldn't turn on?
dunno about the alt key
but if you don't restore from your backup
(did you do a restore at all?
), just use the machine without anything installed, are the alt key and touch screen all ok? if yes then i won't elaborate on my ideas about the touch screen fault
but then list your programs maybe..?
sorry for the many questions but i'm interested...
(in the cause of the problems and the solution
)