Error after upgrading to NW7.3 SPS5 (Enterprise Portal)

Dear Experts,

Could you please help with my problem ?

I've just upgraded our Portal (NW 7.01 SPS6) to NW 7.3 SPS5. It seemed to complete successfully. And the system was restarted successfully with greenlight.

I could log on to the start page with no problem - http://en-adldbp-01:50000/startPage.

But when I clicked on the "SAP NWA" or "System Information" links, then they came with "Internal Server Error 500" and "Details: WebApplicationException log ID is [C0000A40607900440000000400001AF0]."

Would you please advise how to troubleshoot it from here ?

Many thanks

dan