I have always been signing in using my Spotify username and password.
The OS's I am currently using is Windows 7 Home Premium and Windows 8 Pro which are both x64 bit.
My FB friends and their activity feed, and the Spotify activity feed under the "Activity" section of the Desktop App were working perfectly fine until it started happening on Tuesday 1st October 2013. And I did reset my FB password on either Sunday 29th September / Monday 30th September 2013.
Ahah! ~ Now here's what I thought it could have been. Just today I disconnected my FB Account and left it like that for approximately 7 and a half hours. I then closed the App, re-opened the App, and confirmed that it was completely disconnected.
Next, I reconnected my FB account then re-closed the App, re-opened the App again and PING! My FB Friends appear! o_O
Also, I just unfollowed the user that was appearing as their ID number under the "Activity" section and followed another user instead and PING! No more numbers! :D
Now I just re-connected my FB account so I will keep you guys posted if anything goes wrong later on. And once again, thank you so much for all your assistance so far! :D
Edit: It's all back up and running now. Thanks for all your guys support, and sorry for the hastle. :)