To put it simply, there is generally no excuse for non-payment of your assessments.
Whether you have a leak in your unit that has not been fixed, or you disagree with the Board's decision about who was hired to perform the work on a project that necessitated a special assessment, or you feel the Board is acting irresponsibly by implementing a large increase to the annual budget, you are obligated to pay all assessments charged to your unit.
In order to dispute the validity of an assessment that has been charged, an owner would have to prove that the Board acted illegally or failed to adhere to the business judgment rule, which requires only that the Board acts within the scope of its authority in good faith to further a legitimate interest of the condominium.
Read more about this topic (and other legal rulings) on CAI's Law Reporter website.