I had the same error:

InnerException: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index
Message: DotNetNuke.Services.Exceptions.PageLoadException: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index ---> System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index at System.Collections.ArrayList.get_Item(Int32 index) at DotNetNuke.Modules.Repository.Form.btnUpload_Click(Object sender, EventArgs e) at System.Web.UI.WebControls.Button.OnClick(EventArgs e) at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) ---

I've downloaded a new module, installed it and put it on a page.
Then open the page, clicked UPLOAD button , filled the details and clicked Upload button at the bottom. Listed above error occured.
I've found this thread and checked Categories. Categories row was empty.
After reading the documentation, I've opened the module's Settings, and expanded Repository Settings section.
I didn't add any new categories, but when I've tried to upload a new file again, "ALL" checkbox was listed in "Categories" .
Some initalisation of categories list happened between the first and second attempt.

I hope it will help you to re-produce the problem.