2 website windows opening when clicking on hyperlink in pdf

Hi There

Can anyone help?

I created a document in Indesign and have saved it out as a PDF.

I then used Acrobat Pro 8 to add in a hyperlink to web address, and then saved it out again as a pdf.

The problem i have is when i go to view the pdf in Acrobat Reader and I click on the link to test it, two internet explorer windows instead of just one.

One opens and is blank, the other opens the link to the website that i want to use.

I have checked that i have not created 2 links over the top or next to each other, and double checked the web address is correct.

Can someone explain if i am doing something wrong, or is it the way my explorer is set up?

Any help would be grately appreciated.

sarah