What addons do you have installed?
It could be that an addon is repeating the datawriter code...
Liam
My Installed Add-ons
"Stay Logged In" checked by default 1.0.1
-B- Partial IP Search 1.0.0
Add Facebook Login To Visitor Panel 1.0
Add Poll to Existing Threads 1.1.4
Custom Footer customFooter
Daily Statistics 1.2.0
First Post Moderated 1.0.1
Friends by Waindigo 1.0.3
google_adSense 1.0
Join User Group by Waindigo 1.1.2b
Log Out Link by Waindigo 1.0.0
Maximum Daily Personal Converations 1.0
Maximum Guest Views by Waindigo 1.0.0e
Member Card View Permissions 1.0
Monthly Email 1.0.7
Password Protected Nodes 1.1.0
Register Email 1.1
Registration Form Timer 2.0
Self Delete by Waindigo 1.0.0
Smilie Importer by Waindigo 1.0.3
Social 1.0
Template Modification System 1.3.0
View Members Online Now List Guests Restriction 1.0
XenLetter 2.1
XFA - Registration Checks 1.0.0
[8wayRun.Com] XenUtiles (Sitemap) 1.0.1
[bd] Rotating Ads 1.6.2
[bd] Widget Framework 2.4.6d
[Extra LIcense] Unread Threads Counter 1.0.1
[FreddysHouse] Member Page Protection 1.1.1
[Nobita] Custom Usergroups Widget 0.24
[Nobita] XenForo Alert Plus 1.0.5