InTransit,
My experience with some EAD problems is a bit different, but it applies to your question. First of all, as long as your H-1 remains valid, you are fine. Here's my story:
Up to the time when my I-140/I-485 were filed, I had remained pretty ignorant to the process as I worked for a company that fully supported the whole application (company hired an attorney and assumed all the expenses involved). Given that, I'd left everyhing in the hands of my attorney until I had to face problems:
Once I concurrently applied for the I-140/I-485 in September 2002 (EAD and AP applications were sent in at the same time), my lawyer implied I was not to worry about renewing my H-1 (expiring in February 2003) as my I-140 was to be approved within 3 months. At that time, my EAD and AP would be approved. In Januay I sent my attorney an e-mail and reminded him of my upcoming H-1 expiration date. He never responded and I disregarded the expiration of the H-1 assuming that as long as I was on the I-140/I-485 pending status, I was legal as far as presence in the US and ability to work. I come to find out that the former held true not the latter: My presence in the US was legal, but my ability to work wasn't. At that point I was considered out of status.
As I couldn't afford to be without a job and my lawyer realized the seriousness of his overlook -as far as failing to renew my H-1 (my fault as well as far as ignorance and follow up, but it was his responsibility to have handled all paperwork on my behalf to maintain my status), he and I decided to take a chance: I'd continue to work without mentioning to my employer the fact that I had fallen off status until the EAD would get approved.
These are your risks:
1. If found out, you are at the risk of your pending I-485 being revoked and the sponsoring company being fined.
2. If you remain out of status for more than 180 Days but less than a year (meaning, you work without an EAD for that time), at the time of the I-485 review for adjuticaion, you'll be fined $1000.00 but you still get an opportunity to adjustment of status.
3. If you accrue less than 180 Days, you are ok as far as your I-485 being approved without the penalty or risk of being revoked.
I risked it and I only accrued 120 Days. I won't even go into the hell I experienced counting the days and feeling like some kind of criminal by doing what I had to do which was to work to continue supporting myself and praying for the I-140 approval which would trigger the EAD. I never told the sponsoring company. My H-1 expired in February 2003 and my EAD and AP were issued in June 2003 after the I-140 was approved.
Given this experience, I forced my attorney to apply for EAD and AP renewals 4 months (February 2004) before expiration of the ones issued in 2003. This would give me an opportunity to have the local USCIS office issue an interim in case my EAD didn't get approved in 90 days. As I don't have an H-1 anymore, I couldn't afford the risk and the same hell from last year. Thank God I did, as my EAD took exactly 5 months (150 days -last week on 7/9) to get approved this time. But I was able to get an interim to carry me through while I was still waiting for the EAD with the 90 day rule.
So, my advise to you is work without pay until your EAD is approved or take a leave of absence if you can afford any of these two, or risk it if you think you can get away with it based on the size of your company, how strict they are with greencard applicants and your relationship with them.
Best of Luck to you. I can relate to your concern. Let me know if you need any other questions answered.