>> It isn't unlikely that you created a view filter with the Quick Search bar (by giving an enter after the the search condition)
The search mask stays active in other folders too.
You can disable the search mask by pressing Ctrl= or via the menu:
View -> Display -> All messages  <<

roelef, thanks for your help.
I checked the View settings, and it's set at View All Messages, so that isn't the problem.

>>What kind of account are you using?

I'm not sure exactly how I should describe it.
First of all, the account's 'home' is at rogers.com.

My main e-mail account has many 'sub-accounts', or accounts that are 'disposable' type of accounts.
If any of these 'sub-accounts' starts to get lots of SPAM I can just delete the accounts and start a new one.
But my main account remains intact. My main account ends with rogers.com.

The account that I am currently having trouble with is one of the 'sub-accounts'.

'sub-accounts' end with yahoo.ca.

I have set up many filters on my main account.
I found that this was the best way to have the e-mails sorted into the correct sub-account folders.

So for the 'sub-account' that I am having troubles with now, my main account has a filter that says:

Filtering strings:  xxxxxxx-2@yahoo.ca
Location: Anywhere
Presence: Yes

Move messages to \\xxxxxxx-2@yahoo.ca\Inbox

Interestingly, I seem to have this problem only on my notebook, not my desktop (and they are setup the same way).

TIA