Hi and welcome to the forum:
It certainly would be helpful to know the make/model of the computer you're having this problem with. Is it a Desktop PC or a laptop? What version of Windows is this occurring on?
More information about your computer would give us a better chance of helping you.
I've been using WLM since it came out in 2009, and am familiar with all versions.
You can try running the built-in Maintenance for WLM on the message store. This sometimes works, but more often than not a reinstall is required. You can get to this by going to File-->Options-->Mail-->Advanced-->Maintenance-->Clean up now button-->Reset.
If this doesn't work, you'll need to test your pc for virus/malware infection, and consider running Windows repair tools such as CHKDSK & SFC. I might suggest you try these before attempting WLM reinstall, as if your pc is infected with virus/malware, or has Windows system file corruption, it's best to find and remedy these otherwise your WLM reinstall will not fix the problem as it's not inside the WLM app or the WLM message store.
Post back and let us know how that works for you.
Best of luck,
<<<BIGBEARJEDI>>>