You may want to search the forums and also the SoFo site on this topic. There are several articles and many forum posts. My experience and what many others have said is actual dropped frames is frequently the result of capturing to or writing from the root hard drive (almost always C:) If you use a seperate hard drive* the issue of dropped frames usually goes away. Others have reported Vegas saying there were dropped frames when actually there weren't any. Playing the video back, you should be able to tell if there really were dropped frames or just a bogus reporting of same.

* not just a different drive letter, a seperate physical hard drive.