In a blog posting, Redmond said that users who were running Windows XP Service Pack 3 would be unable to remove the browser and install a previous version.
The issue arises when a user installs the SP3 update if they have previously installed the first beta release of Internet Explorer 8.
After installing the recently-released Beta 2 version of IE8, the user will be unable to revert to older versions of IE.
The problem does not affect future upgrades. Although most users would not seek to revert to older versions of software, the issue could potentially affect the work of developers and beta testers of systems in businesses.
To avoid the issue, Microsoft says XP users who have installed SP3 after the IE8 beta 1 release should manually uninstall the browser.
Users of other operating systems are being advised to do the same, although there have been no reports of other operating systems being affected by the downgrade issue.
The problem first came to light this May, with SP3 also preventing IE7 users reverting to IE6.