Me again.
This time a HW issue: today while changing water to my aquarium, I managed to drop my N900 from my shirt pocket (where it was to avoid scratches). Of courcse it went into WC bowl (luckily just plain water). I managed to get it out quickly and removed the battery as fast as I could. Then few hours drying, partly with hair dryer and it is back in business (I am writing this with a washed phone). I hope there will be no faults later on, but I have a bad feeling that me and my N900 will not have a long future together ...