Table structure...very basic:
create table tabla(ID int, Stuff varchar (50));
insert into tabla values(1, '32.43');
insert into tabla values(2, '43.33');
insert into tabla values(3, '23.22');
Query:
SELECT SUM(cast(Stuff as decimal(4,2))) as result FROM tabla
Or, try this:
SELECT SUM(cast(isnull(Stuff,0) as decimal(12,2))) as result FROM tabla
Working on SQLServer 2008