Hello guys (and sorry for my English)! 
I'm working on DotNetNuke 6.0.2 (installed under  NetworkService account on Win 7 Ult, VS 2008 Team system, MSSQL 2005 Dev).
I'm developing a module that collects user information and save data to database. My module has a DnnComBoBox which is hosted by an XmlDatasource control. The XmlDatasource control is bound by an XML file to allow user selects a country and an Xslt file to transform the xml file. I built, packed zip, installed the module succesfully.
When I test the module with Admin or Host account  (in Edit mode) it works fine, and the data is saved as expected. But when I log out or change the site to View Mode, the ComboBox appears strangely: no nav - down button but a "select" link instead, and nothing happen when i click neither select link or entire the combobox, data is not saved ofcourse. I tried to replace the DnnComBoBox with DropDownList control and the control popped up even with anonymous user, but that was it! No data Submit at all, the site gave me  "a critical error has occured..." I created a new portal, then new page and added the module to that page and set the page accessible to every user. I turned back and saw "Permissions" field setting for this module but didn't know what to fill with.
 Did i omit something? Any help would be appreciated, thanks!

I uninstalled the module and reinstalled it and discovered that DotnetNuke notified me something about permission while installing in progress. It could be that ( then my entired module should have problem) ! I'll be off for the code access and permission now and will inform soon !