Mini-Rant:
I can understand a criminal records check, but why do they want a credit check? My personal finances should be none of their business. Does this not violate some privacy rule?

Most pre-employment background checks focus on
a) criminal record check, b) verifying 2 or 3 previous employers, c) verifying education. Typically, credit checks are only done for specific jobs, like handling money, accounting, financial, security, access to hazardous materials, ect. The employer is looking for a pattern of irresponsible or high risk behavior. If you have a problem with your credit record, then you should prepare an honest explanation that shows you in the best light. You can always run a pre-employment background search search on yourself to see what turns up. If the employer discovers negative information, and denies your application, then he must tell about the negative information and where he got it. Then you have a chance to refute errors and get the information corrected.