OK, this subject may sound strange! Why should someone link to a page in the same portal using an URL?

We've built a custom module that requires a parameter in the query string. To achieve this, we've set the link type of the page with this module to "URL", and entered a location like "~/CustomModule/tabid/76/Default.aspx?Param=123".

That works so far, but now we cannot edit the settings of all modules on that page any more. If we try, we get an error message:
"Error: Module is currently unavailable.
DotNetNuke.Services.Exceptions.ModuleLoadException: Object reference not set to an instance of an object. ---> System.NullReferenceException: Object reference not set to an instance of an object."

The only workaround is to set the link type temporarily back to "None".

Does anyone know the reason for this error?
Or has anyone found another way (without side effects) to pass query string paramaters to modules?

[EDIT] We're using DNN 4.5.5

Thanks for the answer! Meanwhile I found out that this error has nothing to do with our custom module. It occurs generally with any module type if you set the page link type to "URL", as described above, even if you don't use query string parameters. I could reproduce the error on a default DNN 4.5.5 installation (on Windows Server 2003 with SQL Server 2000) with the follwing steps:

1. Copy the URL of any DNN page out of the browser's adress bar (e. g. "http://www.domain.com/Home/tabid/58/Default.aspx")
2. Go to the settings of that page, set the LInk URL Type to "URL" and enter the copied URL as "~/Home/tabid/58/Default.aspx" into the Location input field (you may enter the original URL  "http://www.domain.com/Home/tabid/58/Default.aspx" as well - won't help!), and save.
3. Try to edit the settings of any module on that page. Result.
   Error: Module is currently unavailable.
   DotNetNuke.Services.Exceptions.ModuleLoadException: Object reference not set to an instance of an object. ---> System.NullReferenceException: Object reference not set to an instance of an object.

I hesitate to call this a bug because I can understand if you say that linking to pages of the same portal should not be done this way. What's yout opinion?