Yesterday Garmin posted version 4.10 software for the StreetPilot c550. I haven't applied the update yet, so I can't vouch for it, but from the looks of it, there's some fairly significant issues resolved with this update.

Changes made from version 4.00 to 4.10:

* Resolved Address search problems
* Added Brazil and Mexico locale options
* Improved tone generation efficiency
* Resolved lock up issue when setting traffic provider to Auto
* Modified UK, New Zealand and Australia default setting
* Fixed car driving sideways problem
* Fixed issue where scroll up still valid after clearing entries from recent selection page
* Improved GPS reception in long tunnels

The update is available from Garmin's website as an individual download, or can be applied via their WebUpdater software.