The f2c utility and libraries are not included in RH 6.0. While g77 works for most applications, certain things are more functional with f2c. For instance, I have numerical libraries which work fine under f2c but not under g77. After upgrading from 5.2 to 6.0, the version of f2c which came with 5.2 was not fully functional. The problem was fixed by recompiling and reinstalling f2c.
The f2c package has been moved from the Red Hat Linux to the Power Tools distributions. The version that will be in Power Tools 6.0 has been fixed in several ways, so you might want to try that version. Otherwise recompile the f2c from Red Hat 5.2.