I'm on OPT until 12/31/2010. My current employer will sponsor me for an H1B visa.

We found a serious error in the certitied ETA form 9035. The LCA Help Desk informed us that the OFLC would not modify a certified LCA. Therefore, my employer is planning to apply for a new LCA for me to cover the corrections to the errors.

I have two questions regarding this new application.
1. Does my employer have to withdraw the currently certified LCA prior to sending in a new application? If he does, would this case be different from withdrawals due to the end of employment?
2. In addition to the corrections, I'm also thinking to change the employment beginning date from 9/20/2010 (as in the currently certified LCA) to 12/1/2010 in the new application. Would this be okay?

Thanks!