Upload error when uploading a new war file to an ELB instance.

Its very strange. For the last 2 years we have been successfully uploading war files to our Tomcat application running on ELB. 3 days back, the upload process failed with a standard message "Unable to create the Application version". There was no error or reason mentioned in any log file. The only thing I could find was a long list of 401 errors (Unauthorized access) in the f12 browser console at some point in the application upload process.

Once that error occurred, then all other operations with ELB started acting strange for the next few minutes. When you clicked on a link to show the Application under an ELB instance it would show the entire list of ELB instances. If I logged out and in again then it was fine.

After 2 days of futile research, I just tried Chrome instead of Firefox and the error went away. I am using the latest versions of FF and Chrome. So as it stands I still cannot upload our application if I use FF, but it works fine if I use Chrome. Does anybody have any clue on how to make sense of this?!