Problem opening files in Panther

I have been having a problem with opening files on my iMac for a while now. The problem is that it won't let me open files by simply double clicking on the file in the finder or on the desktop. Usually the appropriate program will open but the file will not open so then I have to open the file "manually" by going to the "Open file" command in the "File" drop down menu. I'm also having trouble getting files to open when I drag and drop them on a programs icon in my dock, same thing happens (program opens but I have to open file using the drop down menu). This problem started on my G3 iMac but has migrated to my new G5 iMac (see signature) when I synced them via firewire. My G5 iMac is running in OS 10.3.6 due to printing problems I ran into when I upgraded to 10.3.8. Any help/ suggestions would be greatly appreciated.

Thanks in advance.
rk