A family of Microsoft relational database management systems designed for ease of use.
Milligano,
First of all which version of Project are you using? And, do you have the latest updates installed? (see http://technet.microsoft.com/en-us/office/ee748587).
There are three calendars that can effect when tasks are scheduled - the project calendar (default if the other two calendars are not applicable), the task calendar (if one is created for a task), and the resource calendar (if different than either of the other two). Check all those calendars, if applicable for working days and times.
That's a starting point, then we can go from there if nothing pops out of that review.
John