Fresh install of YAF, only 1 post on the board; click on the post and get the following error, however refresh the page and it will finally display;

parsing "[img=?(\d+)?x?(\d+)?\](.*?)\[/img\]" - Unterminated [] set.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.ArgumentException: parsing "[img=?(\d+)?x?(\d+)?\](.*?)\[/img\]" - Unterminated [] set.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[ArgumentException: parsing "[img=?(\d+)?x?(\d+)?\](.*?)\[/img\]" - Unterminated [] set.]

System.Text.RegularExpressions.RegexParser.ScanCharClass(Boolean caseInsensitive, Boolean scanOnly) +8278645

System.Text.RegularExpressions.RegexParser.CountCaptures() +394

System.Text.RegularExpressions.RegexParser.Parse(String re, RegexOptions op) +126

System.Text.RegularExpressions.Regex..ctor(String pattern, RegexOptions options, TimeSpan matchTimeout, Boolean useCache) +460

System.Text.RegularExpressions.Regex..ctor(String pattern, RegexOptions options) +66

YAF.Core.BBCode.<>c__DisplayClass61_0.b__1(BBCode codeRow) +324

System.Collections.Generic.List`1.ForEach(Action`1 action) +101

YAF.Core.BBCode.BBCode.CreateBBCodeRules(IProcessReplaceRules ruleEngine, Boolean isHtml, Boolean doFormatting, Boolean targetBlankOverride, Boolean useNoFollow, Boolean convertBBQuotes) +6884

YAF.Core.Services.FormatMessage.Format(String message, MessageFlags messageFlags, Boolean targetBlankOverride, DateTime messageLastEdited) +364

YAF.Web.Controls.MessagePostData.RenderMessage(HtmlTextWriter writer) +1412

YAF.Web.Controls.MessagePost.Render(HtmlTextWriter writer) +274

System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +80

System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +169

System.Web.UI.WebControls.WebControl.RenderContents(HtmlTextWriter writer) +15

System.Web.UI.WebControls.WebControl.Render(HtmlTextWriter writer) +50

System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +80

System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +169

System.Web.UI.WebControls.WebControl.RenderContents(HtmlTextWriter writer) +15

System.Web.UI.WebControls.WebControl.Render(HtmlTextWriter writer) +50

System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +80

System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +169

System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +80

System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +169

System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +80

System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +169

System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +80

System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +169

YAF.Core.ForumPage.Render(HtmlTextWriter writer) +30

System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +80

System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +169

YAF.Web.Controls.Forum.Render(HtmlTextWriter writer) +211

System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +80

System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +169

System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) +11661739

YAF.Web.Controls.Form.RenderChildren(HtmlTextWriter writer) +45

System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +47

System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +80

System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) +53

System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +169

System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +47

System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +80

System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +169

System.Web.UI.Page.Render(HtmlTextWriter writer) +40

System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +80

System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4573

The custom bbcode is not part of yaf. You must have created a new one under Admin > Settings > BBCode Extensions. Remove it or fix it so it works