Yes, I confirm that the dates are like 10Aug2011
formatted as General, not as Text.

I'm beginning to think you have more in that cell than the date you are
showing us. I believe you have one or more trailing non-breaking spaces
(ASCII 160) in the cell. Try this and see if it straightens things out.
Select your cell or cells with those "dates", then press CTRL+H to bring up
the Replace dialog box. Put the cursor in the "Find what" field (make sure
the field is empty) and then hold down the ALT key while pressing the
numbers 160 on the NUMBER PAD, not on the main keyboard. Make sure the
"Replace with" field is empty. Next, click the "Options" button to display
all the options for this dialog box (assuming they are not already
displayed) and make sure the "Match entire cell contents" check box is NOT
checked, then click OK. If I am correct in my assumption, then your dates
should have been converted into real dates.

Rick Rothstein (MVP - Excel)