That issue has several resolutions already mentioned in this thread if you bothered to look.
In order of (my) preference:
* Allow TT to access the default save location under "My Documents", which is protected from malware by default. This is done pretty easily via the notification that shows up after you try to save, or by navigating to the Settings ... "Controlled folder access". The Block History link will show a list ordered by date. Couple more clicks and TT is allowed. If you have not exited TT, you can try to save again. No work lost.
* Save in a folder not covered by malware protection (i.e. not under Documents, Music, Videos, Favorites). The tax return file is obviously susceptible to compromise by malware that finds them.
* Disable "Controlled folder access" altogether, which exposes all folders mentioned above.
