DateTime Picker does not work all the times

Hi,
I am using DateTime parameters for SQL 2005 Reports that are converted
from SQL 2000. The report works fine for me but my client complains that the
Datetime pop-up does not come up always on clicking the date button. It comes
up but at times after 3-4 clicks.
Any idea as to why it happens this way?Does your client run pop-up blockers in the web browser?
Perhaps your client's web browser may be running slow; and takes a
longer than usual time to open the datetime pop up. You might suggest
the client to click once and wait for 2-3 mins and see if it fires up.