insert statement does not work

i have a proc.. it is kinda a huge with few temp tables, updates .this used to work fine ..

i have a simple insert at the end of the proc. this doesnt function when i run teh proc.  but will run fine when is run this query seperatly.. beating my head. could some one pls suggest me. is there something i am missing

insert into table select from table where date between @max and @min .. if i remove the parameters and run the proc it works..but not with params included.

so i tried to run the query seperatly with hard code values and also with passing hardcode values using params. it works fine.. suggest please