Sorry, my mistake on cut&paste, here are corrected functions:

void Disable_Interrupts ( void )
{
if (DisableCount == 0x00)
EA = 0;
if (DisableCount != 0xFF)
DisableCount++;
}

void Enable_Interrupts ( void )
{
if (DisableCount != 0x00)
DisableCount--;
if (DisableCount == 0x00)
EA = 1;
}