Bluetooth adapter turned from working fine to unrecognized

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http://askubuntu.com – i had been using bluetooth fine, with devices working, but today when i turned on my computer again bluetooth strangely failed. there is a bluetooth icon on the top bar, showing "bluetooth on", but if i click on the "bluetooth settings" item, a system settings window shows up and shows me a bluetooth on-off switch which is disabled (i.e. fixed to off). more information about my case: i am a new linux used, coming from windows, and do not know supposedly-obvious commands. i am using a laptop. it initially doesn't have bluetooth. i bought a built-in type (instead of USB type) bluetooth modul (HowTos)