I have just installed the new free version, having had previous version. When I first used the new program iy closed itself down after approx 10 secs, did this a few times. So have completely uninstalled Ad-aware and then downloaded and reinstalled it again I still have the same outcome the program opens, I start a scan or a smartscan a scan starts and between 10 and 20 secs the program shuts down, when opened again 'not yet performed' still shows in the 'status' field.
Previous version wa working fine when last used a month or so ago
Any suggestions how I might procede

Try using revouninstaller.com to do the clean uninstall first. When you install again, make sure you've stopped all other applications/processes to avoid any conflicts. There's a chance malware is preventing it from running, in which case you can follow the instructions in my signature. Or, you may be experiencing this bug:

http://www.lavasoftsupport.com/index.php?showtopic=27435