I have a Samsung Galaxy S. I am getting a "Low on space - Internal phone storage is getting low" error.

When I go to Manage Applications it shows the internal memory as 1.9GB used, 6.0 MB Free. When I click "On SD Card" it shows "USB Storage 681 MB Used, 13 GB Free". There is no external SD card in the device.

When I select an app and click "Move to SD Card" it just returns the following error:

Failed to move application. Not enough memory.

Is there any way I can move the apps to the internal USB memory?

Update: I've reset the phone to factory settings so no longer get the error about space getting low and internal storage is almost empty. I've installed a couple of apps and still get the same error when I try migrate them to USB storage.