Hmmm. Not an expert yet, but I think that provider guid belongs to the media items. I dug around in the courier directory on one of our dev sites we have courier installed on. In the files inside this directory: App_Data/courier/cache/revision/media/ I found things like the following xml. Does knowing the problem is in the media directory help at all? Good luck. Have you tried things like clicking on the media in question and resaving them? Maybe something was corrupted?

<Media xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<CourierFileName>3fa1f929-8972-4d0f-b6c0-f0f76af46175</CourierFileName>
<Dependencies>
    <Dependency>
        <IsChild>true</IsChild>
        <ItemId>
            <Id>3fa1f929-8972-4d0f-b6c0-f0f76af46175</Id>
            <ProviderId>e047259a-e73b-11df-9492-0800200c9a66</ProviderId>
        </ItemId>
        <Name>Media Property data</Name>
    </Dependency>
    <Dependency>
        <IsChild>false</IsChild>
        <ItemId>
            <Id>Image</Id>
            <ProviderId>d8e6ad88-e73a-11df-9492-0800200c9a66</ProviderId>
        </ItemId>
        <Name>Media Type: Image</Name>
    </Dependency>
</Dependencies>
<ItemId>
    <Id>3fa1f929-8972-4d0f-b6c0-f0f76af46175</Id>
    <ProviderId>d8e6ad87-e73a-11df-9492-0800200c9a66</ProviderId>
</ItemId>
<Name>Test Name</Name>
<ItemType>Item</ItemType>
<Resources />
<MediaTypeAlias>Image</MediaTypeAlias>
<ParentUniqueId>b08b2039-c4d7-4b17-9bec-559d8db6fb86</ParentUniqueId>
<SortOrder>1</SortOrder>
<Level>2</Level>
<UniqueId>3fa1f929-8972-4d0f-b6c0-f0f76af46175</UniqueId>
<CreateDate>2013-11-01T10:00:13</CreateDate>

Thanks, that did help me find something suspicious-looking. In that media folder there is a file that stands out because its name isn't a GUID, but in that file there is the string:

<CourierFileName>8216d51c-1de3-4eed-99f1-e6de65513bc6</CourierFileName>

The file's name is "media1341465entrepreneurship-d8e6ad87-e73a-11df-9492-0800200c9a66" so I think that Courier has hit upon an issue with this particular file and perhaps can't find it in this folder.

I will try renaming the file to what I think it should be, and see if that fixes the issue

That worked :) I also had to replace this node in the XML file:

<ItemId>
    <Id>/media/1341465/entrepreneurship_-</Id>
    <ProviderId>d8e6ad87-e73a-11df-9492-0800200c9a66</ProviderId>
</ItemId>

->

<ItemId>
    <Id>8216d51c-1de3-4eed-99f1-e6de65513bc6</Id>
    <ProviderId>d8e6ad87-e73a-11df-9492-0800200c9a66</ProviderId>
</ItemId>

Interestingly the original mis-named file got recreated so I assume there is something going on where Courier can't deduce the GUID properly. Anyway it works for me now, hopefully this is useful for someone else (or possibly me when it goes wrong again...)

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