Thanks, Dan. Unfortunately, this code belongs to an external application that needs a way to communicate with Telligent Community remotely, so using the internal API isn't a workable solution in this case. Have you—or anyone—been able to update the <AccountStatus> node using the REST API?
Just FYI, I tried requesting a user's information using the v1 membership API and then sent the unchanged xml back in an update request, but I received the same 403 Forbidden error. For reference, here is the XML that I submitted:
<?xml version="1.0" encoding="utf-8"?>
<User xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" Id="2726" Endpoint="http://oursite.edu/api/membership.ashx/users/2726">
<Username>buckfurrent</Username>
<DisplayName>Tony Buckfurren</DisplayName>
<Signature/>
<Biography><p>I am a virtual sidekick for Robert Miller, the District Webmaster.</p></Biography>
<Points>230</Points>
<JoinDate>2009-09-17T16:40:01-07:00</JoinDate>
<TotalPosts>30</TotalPosts>
<UserRank/>
<RecommendedReading/>
<AvatarUrl>http://oursite.edu/cfs-file.ashx/__key/CommunityServer.Components.Avatars/00.00.00.27.26/4TDQTMUUHREP.jpg</AvatarUrl>
<Occupation/>
<Interests/>
<Birthday xsi:nil="true"/>
<Gender>NotSet</Gender>
<BlogAddress/>
<GalleryAddress/>
<MsnIM/>
<AolIM/>
<YahooIM/>
<IcqIM/>
<Settings>
<Email>foo@yahoo.com</Email>
<EnableEmail>false</EnableEmail>
<EnableNotifications>false</EnableNotifications>
<EnableHtmlEmail>true</EnableHtmlEmail>
<EnableAvatar>true</EnableAvatar>
<EnableCollapsingPanels>true</EnableCollapsingPanels>
<EnableDisplayInMemberList>true</EnableDisplayInMemberList>
<EnableDisplayName>true</EnableDisplayName>
<EnablePrivateMessages>false</EnablePrivateMessages>
<EnableUserAvatars>true</EnableUserAvatars>
<EnableUserSignatures>true</EnableUserSignatures>
<PostSortOrder>Ascending</PostSortOrder>
<FontSize>0</FontSize>
<EnablePostMouseOverPopup>false</EnablePostMouseOverPopup>
<EnableEmoticons>true</EnableEmoticons>
<EnableHelpTipsInControlPanel>true</EnableHelpTipsInControlPanel>
<ItemsPerPageInControlPanel>10</ItemsPerPageInControlPanel>
<TimeZone>-8</TimeZone>
<DateFormat>ddd, MMM d yyyy</DateFormat>
</Settings>
<Roles>http://oursite.edu/api/membership.ashx/users/2726/roles/</Roles>
<Status>
<AccountStatus>Approved</AccountStatus>
<BannedUntil>2010-11-22T12:07:05</BannedUntil>
<BanReason>Other</BanReason>
<IsBanned>false</IsBanned>
<ForceLogin>true</ForceLogin>
<IsAvatarApproved>true</IsAvatarApproved>
<IsIgnored>false</IsIgnored>
<IsModerated>false</IsModerated>
<LastAction/>
<LastActivity>2010-10-22T10:47:20.357</LastActivity>
<LastLogin>2010-11-17T16:18:38.94-08:00</LastLogin>
<MinimumTotalPosts>29</MinimumTotalPosts>
</Status>
<Friends Endpoint="http://oursite.edu/api/membership.ashx/users/2726/friends/"/>
<Announcements Endpoint="http://oursite.edu/api/membership.ashx/users/2726/announcements/"/>
<Comments Endpoint="http://oursite.edu/api/membership.ashx/users/2726/comments/"/>
<Conversations Endpoint="http://oursite.edu/api/membership.ashx/users/2726/conversations/"/>
<ActivityMessages Endpoint="http://oursite.edu/api/membership.ashx/users/2726/activitymessages/"/>
</User>