If you would like to work continuously until August, you must have a work visa (H-1B, L-1 or TN depending on your status) to maintain your status in the United States and to have authorized employment until August. If you need to work continuously until August, ask your employer for petitioning H-1B visa. If your current job position requires bachelor's degree or higher, you will be eligible for applying H-1B visa. Fortunately, H-1B caps are still available as of today.
However, I would like to recommend you to go back your home country once your OPT expires. Your Master's Degree will commence on August, 2011, so you will likely get F-1 visa prior to your degree program starts. But, as a F-1 (unless under CPT or OPT program), you are not allowed to work in the United States.
Thus, getting H-1B or other non-immigration work visas will be the only viable way for you to remain in the United States and to work continuously until August after your OPT expires. If you have any question with regard to OPT program, please visit our firm's website: http://www.sarmientoimmigration.typepad.com.
If your degree is in a STEM field and your employer is enrolled in the EVerify program, you can go to your school and ask for a new I-20 with a recommendation to extend your OPT. Then you will have to file a new I-765 application and wait to get a new EAD. There is a chance that this could be approved by the time your current EAD expires in February. If not, you will have to take a leave of absence from work until the new EAD arrives, which may be 90 days after filing the I-765.