All is not well with Apple's iTunes Match service at the moment — songs that users have uploaded to the service are unavailable for streaming or downloading. You can still stream and download music that was "matched" with content in the iTunes Store, but you can't access unmatched music unless the local file is available on your computer. Strangely enough, this problem appears isolated to the iTunes client itself; when we tested iTunes Match on iOS devices, all uploaded and matched songs are able to be downloaded without issue.
We've confirmed that this issue occurs on both Macs and PCs, and that it occurs on both iTunes 10.5.2 and 10.5.3 (the latest version). This issue occurs on both Snow Leopard as well as Lion 10.7.2; users in Apple's support forums have had the same problem with the ill-fated 10.7.3 update as well. This issue isn't limited to those of us in the US — users in the UK are experiencing the same problems. We're reaching out to Apple for comment and will report back if the company has anything to say — while we don't know for sure, it's possible that the fix Apple is working on for its other iTunes Match issue could be affecting user-uploaded content.
Bryan Bishop, Patrick Austin, Jamie Keene, and Thomas Ricker contributed to this report.