If you encounter some problems & after several attempts still no improvement, try Hard Reset to return to latest flash FW setting. Back up your stuff first before the Hard Reset if you choose to format your Storage.

Option 1

Software Hard Reset:

On your Omnia, go to Settings/System/Hard Reset

Hard Reset options will appear on the screen for

a.Main Memory - Reset
b.My Storage - Reset
c.Storage Card - Format

A pop up will ask for confirmation & user is to enter "1234" to proceed.
The phone resets, lingers on the samsung logo for a bit then the familiar Windows mobile device start up screen, which takes you through the start up process if you tap the screen to set up...
You may have seen this when booting up your phone initially
Alignment
Set date/time
Password

Option 2

Hard Reset using the hard keys:

1.Press soft reset hole beside the power button.
2.Press Call and Cancel Button together when you see the Samsung Omnia on the screen.
3.Reset Screen appear with "Are you sure you want to format? Format or Cancel".
  This hard reset does not erase the 8/16GB memory. To reset everything, use
  the software hard reset > Settings/System/Hard Reset.
  There is also option to format the storage card.

A trick to use for Option 2 - by asctony

1. just lay the omnia on a flat surface,
2. use one hand and two fingers to press (and hold)  SEND and END buttons.
3. use other hand with stylus to soft reset  phone.

Option 3

Hard Reset by dialing code:

Use your Omnia dialing pad & key in

*2767*3855# - doing this will hard reset without warning