I am using 7.3.4, been running the site for couple of years now without problems. Today while uploading a file, the progress bar loads, until full, then i got a an "internal server error" red notification on bottom. checked log, got this error :

ERROR Umbraco.Web.WebApi.Filters.FileUploadCleanupFilterAttribute - Could not acquire actionExecutedContext.Response.Content

Note : I am hosting on "smarterasp.net", also since i moved to them, i am getting strange errors, for instance the cache xml file : umbraco.config suddenly become read only, and the cms will show me errors of "unauthorized access..." so i have to set it to writable in their control pannel to be able to update content.

I know i can simply fix by reuploading from source the whole site but here i am trying to investigate and find what could happened and made these errors happen.