this certainly is a strange situation, one that i dont think has precedence. have you contacted Sage at all? Their support number is 0845 111 55 55.
Software is only usually guaranteed for 90 days, but it may be worthwile taking this up with Sage as a matter of suitability, as you say. Was it a package that was described as, for instance, Sage 2002 or not? If it was you could only really expect it to be valid for that particular calendar year. If not, you should have grounds to take it up with them.