940SE high beam/blown fuses

Can anyone help. I own a 1991 volvo 940 SE. Whilst driving it recently most of the lights went out front and back including high beam/flasher and dashboard illumination. The warning light on the dash came on to let me know that a bulb had blown somewhere. I checked all bulbs but could not find a blown bulb, so i checked the fuses and found a blown fuse. I replaced the fuse and all lights including the dash came back on. Or so i thought. But i found today that my high beam/flasher does not work. Infact when the high beam is on the head lights go out. Ive also noticed that the courtesy light in the car now does not turn off on shutting the doors. Instead i have to turn it off manually or not use it at all. Does anyone have any ideas? All ideas of what the problem could be would be gratefully recieved. Many thanks