JS Error on campaign activity form with custom webresource

Hi,

I have a custom webresource that it's used in other custom activity entities forms without problems, but when I add it to the campaign activity form, na error is thrown with the following description:

Webpage error details

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET4.0C; .NET4.0E)

Timestamp: Mon, 25 Mar 2013 12:13:19 UTC

Message: Object expected

Line: 14

Char: 150

Code: 0

URI: http://win-b5tr96ujk2q/_static/_forms/controls/textarea.htc?ver=1407176682

I checked the file where the error occurs, and the file hasn't been modified and the webresource is a HTML page that doesn't invoke any methods of the textarea.htc file.

The error doesn't affect the overall functionality of the webresource or the entity form, but I'd like to deploy the solution without this error.

Thanks in advance.