Those internet speeds sound pretty good to me. Are you using an older computer?
If your computer is several years old you might be having problems with flash advertisements hogging your CPU. You can check the CPU useage with Windows Task Manager. If that is the problem, you can use a Firefox add-on called Flashblock.
About 3 years old - I did have a crash on New Year’s Day due to a power failure and it acted weird for a week or two after but seemed to fix itself and was fine until now. The funny thing is that my old computer did the same thing after a Windows 98 update and it neevr would run 98 again. XP would work fine though.