[TYPO3-english] Problem Typo3 4.2.2 and Internet Explorer 6, 7, 8

[Justin]

Dear List,

Recently I downloaded the new 4.2.2 version.
I worked all well, but now the website is ready our customer want to edit
the website en fill it with content.

But we are running against a problem that 4.2.2 won't work with the Internet
Explorer versions 6, 7 AND 8!
How can it be that the version is stable and it won't work well with this
browsers?!?!

When iam trying to login with those versions I get this error:
"Your login attempt did not succeed. Make sure to spell your username and
password correctly, including upper/lowercase characters."

And I typed it all well!

When iam trying with the same browser to log in to a Typo3 4.2.0, then it
all works!

So 2 questions:

1. How can it be that a versions like 4.2.2 is stable when it won't work
with updated browsers (and most used in the business "world")
2. How can I downgrade, because now we have the problem the customer MUST
download a browser like Firefox, and we cannot ask every customer to
download this browser, typo3 must work with the most used browsers isn't?

Regards,

Justin