problems with connection

Hi,
can anyone here help (or explain) me?

For about last 2 weeks i have full signal on my notebook (as usual), but buffering, downloading and latency (in wow for example) is deadly slow. I have problem even with buffering an image.
BUT - other computer at home works without problems, same as father's notebook (on same wifi) and mobile devices. I have no problem with connection at school or college (wifi, landline).

Last windows update i did manualy (in that period) is Interface Microsoft .NET Framework 4.5.2 for Windows 7 x64 (KB2901983)

I have visually full connection, but sometimes its not working at all, sometimes it lags, sometimes its just fine as used to be..

Any ideas?