I don't know how to solve your problem with your existing SME install, but you can use FileZilla to recover your files to a workstation, then wipe & reinstall from a 7.3 CD.
hi
this is not the right way..
go to the server-manager web interface and watch your logs files (messages,smbd): there you can find useful infos about your problems
you can also reconfigure your server and verify if it works again..
SME is not windows.. you have not to reinstall it any time something doesn't work..

HTH
Ciao
Stefano