Do they have any record of these 'supposed' warnings and errors? I would ask to see your HR file to see what is in there as well - it is your right to do that. If they are saying that you have had previous warnings then there needs to be records of them and documented evidence.

I would also contact HREOC - Human Rights and Equal Opportunity Commision to find out if what they are doing is illegal or unfair in realtion to getting you dismissed (depends on the size of the company what laws apply to them - and these changed on the 1st Jan so they may also not be aware of this!).