PlusNet modem disconnect - hacked?

[#1]

Yesterday, my PN router disconnected.
I was asked for username & password but this didn't work. Initially, I was unable to access the router in my browser.
Rebooted and it's OK.
What is the likelihood of a router hack via a website virus or a neighbourhood hacker? WPA2 in use IIRC.

[#2]

I'm not going to say there's zero chance of hackers, however from the issue you've described this sounds more like the connection has dropped and the router is asking you to log back in after this.
Your connection logs show a short burst of disconnections on Saturday that may have been the cause.

[#3]

Quote from: Mardler

I was asked for username & password but this didn't work.

Which username & password?  
Assuming you have the TG582n then if Web Browsing Intercept is set to enabled or auto, in the event of the connection being "down" the "intercept" page will prompt you for the PlusNet user connection details... in a screen which looks too darned much like the router admin logon page!  See http://192.168.1.254/helpfiles/b_index.htm?anchor=b_cfg_cfg&file=xml/bConfiguration6.xml for more information.  On this screen, you need the DSL logon details, not the router admin accounts details.
What is more interesting here is why the link is going down or not operating.  DNS look-up failures can give the appearance that the link is down when it is not.  If you see this again, look at the lights on the router before doing anything else and also look (via an explicit connection to 192.168.1.254) at the router log / connection status.  Indeed use the connectivity test here - http://192.168.1.254/cgi/b/connchk/?be=0&l0=2&l1=2&tid=CONN_CHECK1

[#4]

Thanks, Chris. That's what I thought might have happened but the graphic is very interesting. Great service, too.
Townman, yes that's the login screen I got. I'll keep your reply handy! Thanks.