By Tom Finn DOHA, March 3 (Reuters) - Credit cards on the limit, huge bank borrowings and a struggle to repay loans: these are the personal debt problems of some Qataris despite the Gulf state's reputation for fabulous wealth. Generous government salaries and free healthcare, funded by vast natural gas reserves in a country with only about 300,000 citizens, do not always translate into healthy bank balances for ordinary Qataris.