I am sorry to hear about the problem you are facing. You will want to consult with an attorney there locally to determine whether Florida has any specific laws that may help you. However, my thought is that you are unfortunately stuck with the pre-existing limitation. Generally speaking folks have 60 days after they leave a job to elect COBRA which will prevent them from falling into the pre-existing abyss. If you don't elect COBRA and did not have any other insurance, because you were uninsured for that period of time, it appears as though your company is legally within their rights to do what they are doing.
On the positive side, one of the major features of OBAMA-Care is that it eliminates the insurance industries ability to deny coverage based on a pre-existing condition. This doesn't provide you with an immediate solution, but does provide hope for the future.
Good luck. Sorry for the bad news.