Base interest rates may be low in the UK and the US but these rates are not passed on to customers who are in high risk sectors. Man Utd's risk rating will be high. High level of debt, questionable assets - what's the swamp really worth?, if they were to miss Champions League football they'd be in financial crisis.
If they are not paying the interest and adding to the debt then they are living beyond their means - their income could fall as the credit crunch bites - do you think the droves of glory hunters will continue to drive from Exeter and Clacton when they are losing their jobs...
I have always thought that Glaziers escape route would be to float them back on the stock exchange. They will raise nothing like the original (pre Glazier) value of the club (given the debts) but Glazier might walk away with £500m in his back pocket and united will be left with debts of circa £500m on their books. Nice.