There are a number of Outlook Web Access features that don’t work properly in Google Chrome. You can fix most of these with the following fixes, but ideally you should use another browser until Microsoft or Google release a fix that makes OWA and Chrome work together.
To fix most issues, install SilverLight and make the following registry key change:
HKEY_CURRENT_USER\Software\Policies\Google\Chrome\EnableDeprecatedWebPlatformFeatures
Value name: 1
Value type: REG_SZ
Value: ShowModalDialog_EffectiveUntil20400430