Recently we noticed some customers reported that after upgrading to IE9 from IE8, Oiffice communicator can not  download the company address book.

Well, you are not observing this issue in Lync Server/Client environment.

Resolution:

Generally, the ABS file is placed under "https" url, e.g. https://servername/abs/int/files/sample_Company_phone_Number_Normalization_rules.txt.

So here are some actions you should take:

1. Make sure the option "Do not save the encrypted pages to disk" is unchecked.

    The option is under "Internet Options" -> Advanced -> Security.

2. De-selecting the option "Enable Integrated Windows Authentication".

The option is under "Internet Options" -> Advanced -> Security.

More references:

http://blogs.msdn.com/b/scottos/archive/2008/10/16/why-is-communicator-prompting-me-for-credentials.aspx