i'm running ubuntu on my laptop.

first i connected it via the default n900-bluetooth functionality - not bluemaemo (hadn't it installed at this point). it was recognized as "phone" by my laptop and so i only had access to the phone-functions and mass-storage.
then i installed bluemaemo and the hid-functions didn't work at all. (no wonder because it was still registered as "phone" by my laptop and the list of functions wasn't updated)

so i deleted the paired connection on my laptop and my n900 and started them to pair via bluemaemo the way i discribed above. it wasn't recognized as "phone" anymore. it was in the "other" category.

i paired them and the connection was established.
but as soon as i ran a function at bluemaemo on my phone it was disconnected. tried several times via the reconnect-button but i had no luck.

when i had some time off i had to give it another try. so i deactivated bluetooth on both devices. (maybe at that point a reboot could help?! and after that...) started bluemaemo on phone with "wait for connection...". then started bluetooth on pc and searched for devices. connected to n900 and paired them. then the function-screen came up and i tested the mouse. it worked.
(yeah... really strange... but the only thing i can say... if it doesn't work on the first attempt... try again... and again.... aaaaaaaaand again... ^^)