Open the folder where you installed phpMyAdmin and make sure that all the files end in your php extension.. For example, if you use PHP3, the should all end in .php3.
If they don't, DO NOT change them manually. This will not help the situation, as the references to files are hard-coded in to the scripts. Instead, download the latest phpMyAdmin from http://phpMyAdmin.sourceforge.net that has the apropriate file endings. You will need to reconfigure it, but it should work.
Hope this solves the problem!