Malware is definitely a possibility from they way you describe the problem. If you use Firefox all the time rather than MS IE, you have a much lower chance of ending up with malware installed though.
The reason I asked about whether a shortcut to a URL works is that Windows treats URLs and html files differently. When you open an html file, either directly or with a shortcut pointing to the file, Windows opens it according to the settings for .htm files in your file types settings. When you open a URL, the settings used are the one for that particular type of URL. Generally, most people want the settings for .htm files and http and https URLS to be the same, but sometimes one or more of them end up with messed up settings. The fact that this happened when you installed a new version of your browser points to a problem with those settings as a possibility. Malware has been known to alter those settings as well.
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The reason I asked about whether a shortcut to a URL works is that Windows treats URLs and html files differently. When you open an html file, either directly or with a shortcut pointing to the file, Windows opens it according to the settings for .htm files in your file types settings. When you open a URL, the settings used are the one for that particular type of URL. Generally, most people want the settings for .htm files and http and https URLS to be the same, but sometimes one or more of them end up with messed up settings. The fact that this happened when you installed a new version of your browser points to a problem with those settings as a possibility. Malware has been known to alter those settings as well.