We are for the moment on ROLLUP 11 with CRM 2011 and we're encountering a weird problem with the CRM when using Windows 8 and IE 10. We've added the CRM URL in the "Comptability Settings", otherwise the lookups don't work...
When you click on a subgrid in an entity (all entities gave an error) and you click on "Add New ..." and then you create your item. Afterwards you click on "Save" or "Save & Close" then the screen won't close (in case of "Save & Close") and an "Error"-message will be shown on the page where the subgrid resides. (Same happens on "Save")
It's a typical "An Error Has Occured"-error, but with the "Download LogFile"-button greyed out. When you click on "OK" in the "Error"-message, then you are able to close the page of the new Item and it is also added to the subgrid. I think, it's when you Refresh the subgrid (by adding the item), the error happens.
I tried to use developer tools, to see what could go wrong, but it didn't even show me the error...
Everything works as it should on my Windows 7 with IE 10. I was able to reproduce the error on several PC's with windows 8 and IE 10.