Are assessments for specific repair or maintenance projects?

Do special assessments have to be for a specific common area maintenance project? Our board charged home owners with a $1900 special assessment because 50% of the units were not paying their monthly dues. I have refused to pay this assessment and now I am being sent collection letters stating that they will place a lien on my property. I have requested to see the minutes time and time again to determine the purpose of the assessment but have been ignored. What are my rights?