Answer
The problem is caused by a setting in Internet Explorer – this setting seems to have changed with the upgrade to IE7, i.e. it is not an issue in earlier versions of Internet Explorer.
To resolve this issue you will need to open IE7 and go to the "Tools > Internet Options > Security" option, select the zone your GMS Webmail server is in (normally Internet) then click on "Custom Level".
You now need to change the option for "Automatic prompting for file downloads" to "Enabled".
You should now find that attachments open with out further problems.
As an alternative you can change the preferences in Reading Mail in GMS Webmail to not show attachments as a drop down. This will instead show them as a normal in-line link which you can click on in the normal way.
Keywords:attachments IE7 Internet Explorer 7