I just had a case come up with my Aggregator module and some of the modules rendered within it. For some modules I need to inject them on the Init event instead of the load event and in some of these cases the module menu for the injected modules seems to render at 0,0.
For instance, here is some of the html I found by looking at it through FireBug:
<table cellspacing="0" cellpadding="0" border="0" id="dnn_ctr370_Aggregator_ctr369_dnnACTIONS_ctldnnACTIONSsub21" style="position: absolute; top: 0px; left: 0px; display: none;" class="ModuleTitle_SubMenu">
Is there a reason you can think of that it would choose 0,0 rather than the correct position of the module?
Here is a way you can reproduce in case you have time to test:
1. Install the Aggregator Demo module located here, http://www.dnnstuff.com/Download/tabid/298/view/topic/postid/1372/forumid/15/language/en-US/Default.aspx#1372
2. Add the Aggregator to a page
3. Add a text/html module to the page
4. Add the text/html module into the Aggregator through Edit Tabs, Add an Existing Module to a Tab
5. Update the Aggregator settings and you should see the text module inside the tab
If you hover over the menu for the html/text module it should drop down properly in the correct place.
Now, if you go to the Module Definition for the Html/Text module and select the 'Supports Partial Rendering' option for that module and save, then go back to the previous page and hover over the menu for the html/text module you'll see that it renders in the top left position of the browser window.
If you have any questions or need me to try anything please let me know.