dryantd,
As ALawyer said, you should get some professional help as there are many outstanding questions and issues to be resolved and considered:
1.Typically, the disability will be covered if the coverage terminates after a qualified disability has begun, and benefits will be paid according to the plan term, even though the coverage has cancelled. The premiums you pay are to cover "a disability that begins while the coverage is in force" and are payable as long as that disability continues, until the end of the coverage period.
2. Typically, employer based insurance terminates when your employment terminates and is not convertable. Are you still employed? If you pay the back premiums, will the coverage actually be continued according to the plan terms? Is it possible that your employer should have terminated coverage (according to the plan terms and their general employment practices) and is now trying to recoup premiums they should not have paid? If permanently disabled, do you really need to continue the coverage?
3. Typically, employer based disability coverage that extends for more that 6-12 months is referred to as Long Term Disability (LTD) and disability benefits are payable to age 65 or lifetime, depending on the plan.
Many of these questions can be answered by a careful review and understanding of you disability policy/plan document and your "Employee Handbook".