Homeowners across the U.S. are increasingly having trouble making their mortgage payments on time, but borrowers in metro areas of California, Florida and other once-booming housing markets are accounting for the biggest spikes in foreclosure filings, according to a mortgage research company.An analysis of foreclosure activity in the nation's largest 100 metropolitan areas during the three months ended Sept. 30 shows seven cities in California and five each in Florida and Ohio were among the top 25 metro areas with the highest foreclosure rates, according to the study being released Wednesday by RealtyTrac Inc. Mercury News