Konical has it just about right if all your ruined shots were flash. On your speed dial, there is a number in a different color (I am betting). For flash syncronization, you need to shoot below that number. This number is usually 60 or 125 (250 if you shoot a Nikon FM2n). Anyhow, Try another roll, ASA 200 or so, we are not talking major investment here, and shoot at 1/60, use the flash to determine aperture.
Don't worry, 20 years? You've just forgotten a thing or two.
tim in san jose (15 years till retirement)