Can't Close My Computer Case!

I have a Dell Dimension 8200 and recently I had to open it to install a Firewire card. It all went OK until I tried to close the PC back again. No matter how hard I tried I could only get one side of it to 'click" back into place. I tried for a couple of hours working up a literal sweat and finally just gave up and set it right side up again so that essentially it's only half closed. Does anyone have any ideas other than to just keep trying. Have you noticed what an awkward process opening/closing one of these things is? It feels or seems like the majority of the weight of the machine is the lid itself that your trying to raise and lower back into place. Anyone else ever had this problem? I'm also afraid I may have damaged the click-back-into-place -mechanism so that it might not go back into place from those two hours of aggresive wrestling with the thing. Anyway the PC is working fine...so maybe it's ok to leave it that way for now...