When viewing properties on some of our events, a pop up box appears stating:

Specified argument was out of range of valid values.

Parameter name: '-1' is not a valid value for 'index'.

 This happens in all of our applications, so its not just a case of a single bug having being copied multiple times within an application. There doesnt seem any problem with the code - its runs fine afaik. Any one else seen this and any ideas what it means? Thanks