Just got this email from Ulster Ancestry..
The Monoghan tables seem to be having a problem, but the other counties seem to be OK.Free Ancestor Search now on line.
All family history research in Ireland starts with Griffith’s Valuation
The Primary Valuation of Ireland, 1848-1864, gives a complete list of occupiers of land, tenements and houses. Better known as Griffith's Valuation, it is arranged by counties and within counties by Poor Law Union Divisions and within Unions by barony and then by parish and townland.
You can now search the Valuation for all 9 Ulster Counties for Free at http://www.ulsterancestry.com/search.html
Good luck and good hunting!