Input string was not in a correct format.

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

[FormatException: Input string was not in a correct format.]
   System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) +7476535
   System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) +119
   System.Convert.ToInt32(String value) +63
   Infragistics.WebUI.UltraWebListbar.UltraWebListbar.getRenderer() +320
   Infragistics.WebUI.UltraWebListbar.UltraWebListbar.PreRenderLBar(Object sender, EventArgs e) +20
   System.Web.UI.Control.OnPreRender(EventArgs e) +8766646
   System.Web.UI.Control.PreRenderRecursiveInternal() +80
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +842

I had an application in Win server 2008 that had a reference to Infragistics 5.2 dll but Infragistics was not installed in the machine, I installed Infragistics v6.2 in the same machine and I started getting that error, I even uninstalled Infragistics but still get the same error. I tried installing version 5.2 in the machine but error doesn't go away. I believe the machine did not had infragistics but installing it in that machine introduced the error now it doesn't go away.Can anyone please help me I have been stuck on this issue for last 3 days.