How to not wait for USB to become active?
After you post your code this answer may not apply.  But, guessing, you may benefit from changing your code from:

loop()
{
 data = Serial.read();
 // Do other sutff
}


To something like this:

loop()
{
 if(Serial.available() &gt; 1)
 {
  data = Serial.read();
 }
 // Do other stuff
}