A working metronome can be obtained as follows:

On the n810: (I guess it will work on others too)

1) Visit this web site: http://www.metronomeonline.com
2) Menu -> Web page -> Save as -> (Type = Complete web page)
3) Using the filemanager, visit the directory where you saved it.
4) Browse through the directory and you will find a Flash file called "metronome"
5) double-click on this Flash file and a web browser will open with a working metronome. (A warning will appear, just click OK).

(You can delete all the other files, only the Flash file is required).