.NET Compact Framework 3.5 conversion Got_Focus error

We are currently migrating a PDA application from .NET compact framework 1.1 to .NET compact framework 3.5.
PDA having operating system Windows 6.0 and 6.5 installed
On got_focus event of custom text box we have wrote below code

private void tbCustom_GotFocus(object sender, EventArgs e)
{ 
    m_Keypad.SetBuffer(tbMileage.Text);
    m_Keypad.HideOSKeyPad();
    m_Keypad.Show();
    this.m_ToolBarButtonNumericKeypad.ImageIndex = 11;
    tbCustom.Focus();
}

its working fine in .NET CF 1.1 but while we convert this code into 3.5 without changing any code its just got into recursive and applcaiton is got crash. Please provide help about this. Thanks in advance.