Recently diagnosed w/immune disease. Bloodwork showed ESR rate of 11.9 in dec '11, 2 weeks ago it was 142.2 what could this mean & how serious is 142.2?

Elevated ESR. The ESR blood test is a marker for systemic inflammation. For most laboratories, the normal range is less than 20 for men and less than 30 for women. With a significant inflammatory process, this goes up to the 100-150 range. An abnormal ESR by itself does no harm. It just means that an inflammatory process has been activated. The goal is to treat the process that is causing the inflammation.
Quite elevated. An ESR of 142 is extremely high and needs to be worked up fairly quickly. Since I do not know your symptoms, the change in the values suggest processes that are inflammtory to infectious. Your physician or physicians need to be doing tests on you quickly and yes it could be serious.