Internet explorer problems????

Internet explorer problems????

Hi,

My users are having problems since january 2010.
Problems:

- when submiting they dont receive the confirmation message and the internet explorer opens an pop up suggesting to download .do file...
- the data field is not opening, they have to write instead of using the calendar pop up

I use a mac os with safari, and I dont have problems

is it a internet explorer problem??
Please fix it to me....

thanks