I would recommend the following:
1. Check that you have the most recent version of both Viewer and Host. This should be 126.96.36.199 as of this writing. There used to be issues with previous versions and Windows update, as described in this article
2. If there is antivirus software on the Host computer, make sure you add the Host installation path to its exception list. This is recommended even if you don't have issues with this a/v software so far - you never know when they decide to block or restrict the software next time. A/V programs don't like remote controls much and often mark such programs as riskware.
Specifically about Symantec - there were couple of issues with them recently and each time we reported to Symantec. The last time they responded that the issue was fixed. But if you still have issues with Host settings erased or reset - and this is a sure sign of either a/v activity or Windows update activity - then let us know.