[logfromblammo]

I think the problem may be with those who intend to apply for permanent residency while legally present on an H1B.

Once you apply for a green card, you have to maintain legal immigration status continuously. Furthermore, nationals of India and China have to wait longer, due to country quotas and relative demand. There is something called a priority date, which is somewhat akin to taking a number instead of waiting on queue, except it's really more like a number for the secondary queue to get a number for the real queue.

There is an I-140 form that is part of the process, which is filed by the employer. If this form is withdrawn, perhaps in response to changing jobs, it can reset priority dates or cause extensions to be denied.

[hpagey]

i-140 can transferred between employers and you retain your PD. Typically, sponsoring companies do not revoke i-140.

[e15ctr0n]

The previous employer can choose to withdraw the I-140 petition, and typically does so because keeping I-140 petitions around for ex-employees can create problems for the I-140 petitions of current and potential new employees.