I looked at a property yesterday with a realtor who quite obviously has no clue what he is doing. I really want to purchase that house, but don't want the hassle of working with an agent who doesn't know his business. Can I switch agents and still buy that house?
If you want to purchase that property, the only ethical thing is to purchase it through that Realtor. Otherwise, you could set up potential conflicts between your previous agent and whatever new agent you may choose.
You see, if your previous agent finds out you purchased the home with a new agent, he may want to claim all or a portion of you new agent's commission. This could develop into a "battle royale" involving real estate agents, offices, managers, brokers, and attorneys.
You may be able to resolve the issue by letting your current agent know you have misgivings about their expertise and ask if a more experienced Realtor from his office can be aboard as your advisor, too.
That is the only ethical way I can think of to handle your situation. It isn't "your" ethics I mean, but the ethics of the two agents. One agent isn't supposed to make an offer on a property you have already previewed with another agent. It happens, but it isn't ethical without some sort of disclosure and agreement between the parties.