For some weird reason, YouTube's announcement system
of new messages sometimes reverts back to the last time
when people checked their messages.
Have you noticed that the "number" which YouTube claims
are your newest messages is the same number as the last
time you "opened" your previous messages?
Sometimes, the very same thing happens to those people
who receive notices about the number of "new subscribers"
they supposedly have. This "glitch" has been going on for
quite a considerable time.
One thing you could try and do is clear all of your cookies,
history and temporary internet files. In doing that, not only
will your computer seem fresh in YouTube's eyes, perhaps
their display of messages will reset and be more accurate.
After doing one of the sequences below, shutdown/reboot:
Internet Explorer 6:
→ Tools → Internet Options
→ Delete Cookies → OK
→ Delete Files → OK
→ Clear History → Yes
→ OK
Internet Explorer 7:
→ Tools → Internet Options → Delete...
→ Delete files → Yes
→ Delete cookies → OK
→ Delete history → OK
→ Close (browsing history window)
→ OK
Internet Explorer 8
→ Tools → Delete Browsing History
[. ] Preserve Favorites (leave blank)
[x] Temporary Internet files
[x] Cookies
[x] History
→ Delete
Mozilla Firefox 3:
→ Tools → Clear Private Data
[x] Browsing History
[x] Download History
[x] Saved Form and Search History
[x] Cache
[x] Cookies
→ Clear Private Data Now
Apple Safari 3:
→ Edit → Preferences
→ Security (tab) → Show Cookies
→ Remove All → Done
after that:
→ Safari → Empty Cache → Empty
after that:
→ History → Clear History
Google Chrome:
→ Tools (wrench) → Clear browsing data...
[x] Clear browsing history
[x] Clear download history
[x] Empty the cache
[x] Delete cookies
Clear data from this period: → Everything
→ Clear Browsing Data
The other thing that you can try is opening the messages
several times back-and-forth. A few people here on Yahoo
have written that this helps make the messages "unbold".
After doing that, click the envelope icon a few times. This
double process could finally bring about the much-desired
0 unread messages. You might also want to try going to
your "video responses" or "friends invites" and then going
back to your "inbox".
There is also the possibility that your inbox is way too full.
(Please disregard this if you don't have many messages).
Try deleting some of your oldest messages. If you want to
keep them, copy-&-paste them into a "Word" or "Notepad"
file. This solution has apparently worked for a few people.