As some have suggested, I think that sometimes a creative explaination is quite easy to spot by a recruiter.
It's a really difficult situation for you though as people who are employed view self employment as a warm sunny place where everything is glorious and you spend all day watching daytime TV. The reality of self employment is that the hours are longer, the stress is higher and cashflow can be fantastic at times yet sticky at other times.
I don't know how you could phrase it, but my suggestion would be to be loud and proud about your successful times self employed. Let's face it, for more than 4 years you were successful, but due to circumstance and a client of yours going under and oweing you, you have had to call it a day. Small business has really suffered in 2009 and credit lines have been pulled by banks. 2 years ago if you had had a set back, there would have been a chance that a bank would have been prepared to cashflow your business until you caught back up again.
My suggestion would be to focus on the success and lead into how you are positive about the situation and moving forwards in your career, and that your new employer will benefit from your huge experience gained. You are 'probably' easier to work with now than before as you have had to be more adaptable over the recent years.
I don't think there's any harm in suggesting that employment is a 2 way street and that nobody is doing anybody any favours for the sake of it, it is a business transaction, you are exchanging your experience and skill for more stable and less erratic cashflow, and the employer is gaining someone with huge skill probably for less money than that skill level deserves. There are possible trade-offs for you both, but you are exchanging positive benefits with each other.
I would try not to put too much detail in the CV, but attach a killer covering letter that is very specific to the company. Do some research on them and let your cover letter inform them that you understand more about their business than all the other applicants.
What do you do out of interest?
Good luck.
Stu.