"False positive" is the term for it. Flash Player conatins no virus.
There has been a rash of "repairware" lately, that attempts to steer people to unscrupulous sites to "fix" what they put on your computer in the first place. It often will disable your antivirus, and EVERYTHING you try to download is suddenyl flagged as "containing a virus" sometimes with a link to "Fix this now".
Run a thorough scan of your system and if need be download TDSSKIller from Kaspersky to check for other trojans.
Download the Adobe Flash Player installer directly by right clicking one of the following links and seelcting "Save target as" or "Save link as".
Save them, and THEN run them. If you see a "virus" warning with either download, that'll be proof that your system is compromised.