Hi @sugerbea ,
I realize that it may be difficult but can you tell exactly which ones blink and which ones are steady, looking from left to right.
Getting that information will help diagnose the problem as the sequence of which is flashing and which is on steady gives an error code which will help to point out the problem area.
Here is a link to the [http://downloads.dell.com/manuals/all-products/esuprt_laptop/esuprt_latitude_laptop/latitude-e6400_service%20manual_en-us.pdf|service manual] for your laptop. Click on the ''Troubleshooting'' link to view what the Diagnostic Light Codes during POST pattern reveals regarding the problem