Welcome to the forums.
Your profile says you have a curve, but you need to be more specific, do you have an 8300, 8310,8320,8330,8530,9330, etc?
The 8320 OS will only work with the 8320 and so on. You need to make sure you download the appropriate OS for your device.
Once you download the correct OS (if you haven't), then follow these steps to the letter.
What to do next if Jl Cmder will not connect and wipe - BlackBerryFAQ