I have looked around for an answer to this question and couldn't find it. Weird, since I know I saw it on the site somewhere before!
We were out trying to find a cache this weekend and were getting seemingly erratic readings. Then, a huge cloud cover rolled in and we started getting readings that were off by 80 feet. Next, no signal!
I am using a Garmin eTrex Legend, if that helps.
Thanks for you answers,
- netgeist