slow down at the end of songs

this's been happening to me lately, since i just started playing again. at the end of songs sometimes (it's happened in both firefox and ie) the arrows slow down so i do not hit them correctly, even though i should be. i wanted to know if this was a known issue, or if anyone else was experiencing it (check both the faq and searched the forum but found nothing). thanks for the help in advance! ^_^

edit: noticed other post, read all the way down, person didn't go into any detail in their post, and there's no answer in it. so delete this if you want, but i'd still like an answer