buffering problems

i just bought this computer (acer, windows vista) about a month ago, we got dsl internet through at&t (w/motorola modem) about a week later. for the first week or so, i didnt have any problems with anything, but then, my adobe flash player started messing up, saying buffering every five to ten seconds, throughout any complete video, and has been doing it ever since. since then ive installed new spyware and everything to keep my computer clean and protected, but it still does it. ive also uninstalled flash player and installed it again, but still the same buffering crap. i was wondering if it was my computer (which would really suck because its brand new) or my internet connection, please somebody help me out, thank you very much