My N900 is bought together anextra battery in June. I have this habit to swap the batteries weekly. It did not ask me to set date & time until yesterday.

Yesterday I upgraded the browser from Firefox Mobile to Firefox 4. I found Firefox 4 very slow; it took forever to load a web page. I uninstalled & reinstalled it but no help to its performamce. Then, for some reason, I went into Setting and tried to access the ProfileMamagerX, for the 1st time, I obtained a error message - "Internal Error ........". So I decided to soft reset it by switching off and removed the battery for some seconds and then turned it back on. Starting from that time, N900 asks me to set time & date. Besides, its ringtone also resets to default "Nokia tone" but it does not reset the customized tone for SMS.

I guess this is not a back up battery issue but caused by software conflict.

TC