855 taking long time to 'discover' satellites

My nuvi 360 did took a while to find satellites for almost 2 days in a row a week ago...both with heavy clouds cover here.

Must be the weather.

When was the last time you had the unit in use?

How far away were you from the place you last turned the unit off?

Neither of my units had problems find satellites recently.

I use the unit daily; doesn't matter if I'm at the same place I turned it off or elsewhere.

Clean out the track files and any extraneous data you have on the unit such as Favorites you no longer need. You could be running out of memory and the unit is having to shuffle data around because there isn't enough free space. You DO NOT NEED TO REORGANIZE THE STORAGE!. It won't make it any faster.

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Is there an easy to delete entries in All Favourites, other than select/Edit/Delete/Yes for each one?

You should be able to select multiple entries when in the edit mode.

Just delete the Current file on the unit. It will create a blank file at start up.

The OP may benefit from a hard reset as well. It will delete the Faves file at the same time.

My preferred way is

Tools > (scroll down) > My Data > Delete Selected Favorites.

This allows you to put a check by the Favorites you want to get rid of and delete them all at once.

Using which program/editor?

As already stated, but clearer. Hook the gps to the computer. Locate the current.gpx file and delete it. Restart the nuvi and a new current.gpx will be created but it will be empty.

The othere way is through the nuvi go to Tools > (scroll down) > My Data > Delete Selected Favorites.

Current.GPX is a copy of the data stored in protected data. Deleting it does nothing to the data stored in the protected area. The only way to delete the data is to go through tools.

There are several ways to delete Favorites/Saved Places entirely.
1. Do a Master Reset.
http://www.poi-factory.com/node/30019
2. Use Tools on some devices
on my 765T Tools (wrench) > My Data > Delete Favorite(s)
where I can choose "Select All" or put a check mark beside some of the favorites. Then Delete > Yes.
3. Use Where To? on some devices
On my 2595 Where To? > Saved > [triple bars at top left] > Delete Saved Places where I can choose "Select All" or put a check mark beside some of the Saved Places. Then Delete > Yes

Just to reiterate what has already been said: Current.gpx is an "output only" file.

If you look at your GarminDevice.xml file and find the reference to Current.gpx, it will say

Mission accomplished.
Thanks all for your assistance