For business lines of credit, the key position seems to be the CFO. All of the lenders look at the CFO and the CFO has to sign for any credit (though after 18-24 months the CFO can usually be taken off).
This means that it doesn't really matter what your credit history is. You just need to partner with someone who has good credit. Note that the CFO will be responsible for the debts of the company so make sure that the CFO is comfortable with that risk and believes in the ability of the company.
As I stated above, the CFO is only at risk for the first two years. After that, if the business is doing well, the CFO can usually get his name off the loan. That means that this will only be a 2 year risk for him.