Problem opening a Report

We're using Crystal Reports 2008 on a Windows Server 2003.

In our sofware written in Visual Studio 2008 sometimes it happens that "LOAD(ReportName)" statement it takes MANY seconds..... and other times it takes few seconds.

The same thing happens to some our clients... and we dont understand--- WHY???

Can you tell me something about it??

Regards

Fabio Zucchelli