Can't connect to my home network

Hi all, First time posting here - any input would be greatly appreciated. I've just moved into a new apt and internet has be installed so all apts in the house can use it. The first day i connected no problem at all (wifi - no cable) - entered the security key i was given and same worked fine for the evening. I took my laptop to work the next day where i also use both wifi and cable connection - (wifi works fine in the family home and other friends houses too) again same was working fine. When i got home i tried to establish a connection with no luck. My flatmate was on his computer and getting a good connection. I tried all the diagnostic tools but was still unable to get online.....i've since come back into work today and both wifi and cable connnections are working fine. - basically i was advised there was limited connectivity on the home network (even though signal was good and like i said my friend was sitting close by working away online on his laptop).........i'm at a loss to why this is - if same was happening in different places i'd blame the comp. or if i hadn't been able to connect the night before i'd blame the connection........tried resetting network adaptor/deleting connection and starting again - none is working - it seems my computer wont let me connect to that particular network (although it did the night before and does in other locations) - i don't get it! - again any help on this would be greatly appreciated..thanks