Is 30 minutes enough time to change terminals in Houston?

Q: We booked our flights from SFO to London using Delta SkyMiles and were put on Continental flights thru Houston.  The SFO to Houston leg was changed slightly giving us only a 30 minute connection in Houston.  I called Continental about my concern over the very short connect time to go from domestic terminal C to International E in only 30 minutes.  They said that 30 minutes was the minimum connect time and we should probably make it.

There is an earlier flight from SFO to Houston which would give us 1 ½ hour connect time but since there were no frequent flier seats on it they would not rebook us on the earlier flight.

Do you have any suggestions on how to book seats on the earlier flight other than trying to go standby which is our plan?

A: No, 30 minutes is probably not enough time to make that connection, what is Continental thinking? Especially if the incoming flight is late.  I would keep calling the OnePass service desk (at least once a day) trying to get an earlier flight into Houston (any earlier flight, not just the one with 90 minutes connection time) using miles. Ask to speak to a supervisor and explain the situation. Even if you were somehow to make the tight connection, you'd be so frazzled that it would take you 24 hours to recover! When last we checked, standby travel is not allowed on Continental frequent flyer tickets, although this may have changed (other airlines allow this but charge up to $50 per passenger).