it may be a spyware/malware program already running which recognises spybot and shuts it down. download the latest updates and run them to install them, manually. try again in safe mode. also, try adaware
www.lavasoft.de if that diasplays the same sort of behaviour, then malware is probably responsible. if it runs okay, should take a few minutes to scan, then see if spybot will run after you clean whatever adaware comes up with. if spybot can run okay after adaware, then it probably was malware. use the latest updates for adaware, too.