A CRJ200's right engine 10th stage bleed closed and the right pack tripped OFF at 8;000 FT resulting in loss of pressurization because the left pack and APU were MEL'ed. The bleed and pack switches were recycled to restore pressurization.

Narrative

The aircraft had a deferred APU and a deferred left pack. I was already hesitant to take this plane with this combination of deferrals. The flight to our filed destination [had] very high workload but uneventful. On the flight from the airport; we did an unpressurized takeoff per the MEL. The takeoff was uneventful. We were cleared to climb to 7;000 FT. Leveled off there because of same direction traffic at 8;000. We acquired visual with the traffic 3 miles way from us and were told to maintain visual and continue the climb. As the power levers were advanced; we could feel the air conditioning fail. I looked at the EICAS and saw right pack off. There was no associate pack over press message; just right pack off. I looked at the ECS page and saw that the right pack was off and the 10th stage bleed was showing closed. Because there was no caution; there was no QRH page to refer to. I decided that we needed to try to reset the ECS. I commanded the 10th stage bleed closed and then open again. This worked. I then cycled the right pack and it came back on. When we landed and opened the thrust reversers; the same thing happened again. We taxied in with the pack off. This was a threat in that we lost pressurization at 8;000 for about 30 seconds. We were also tasked with keeping visual separation with the other traffic. While we did not lose separation; we did stop looking for the traffic as we dealt with this issue. Aircraft should never be dispatched with a deferred APU and a deferred pack. The workload dictated by the MEL and QRH is just too demanding.