Serious issue was found with 0.4.4.6 installation packages, those installers could function improperly on some systems. So, installation packages were replaced with corrected ones.

64-bit installer replaced, sha1 sum of the correct file is 8a8eac4c2abd70e94520014dfe67faa63945e2c3
32-bit installer replaced, sha1 sum of the correct file is ae600c0df9f5367787ff1ba9a401e3858005ee70

You can verify sha1sum of your file using QuickHash utility:
https://sourceforge.net/projects/quickhash/

If you have downloaded a new installation package recently then it’s highly recommended to check your client version (see Help -> Debug window). If it’s 0.4.4.6 then you can ignore this message, otherwise you need to download a corrected package and install it as usual.

P.S. Don’t forget to remove the old blockchain database files while upgrading to 0.4.4.6 version.