In a down market, you may have to consider lowering your price and/or making a major repair, such as replacing the roof, in order to lure a buyer. Also, make sure that your home is getting the exposure it deserves through open houses, broker open houses, advertising, good signage and a listing on the local multiple listing service or online listings provider.
If this isn't happening, take it up with your agent or agent's broker. If you are still not satisfied you are getting the service you need, you may have to switch agents.