Should I be concerned?

Hello:

After recently installing Avast, I am getting repeated alerts for files in my dropbox folder on my Mac. Someone on that forum suggested this was a false positive and to create an exception, but a) what if it is a threat and b) can’t figure out how to create an exception for a hidden file.

The alert says the infection is: PHP:Decode-DL [Tri}] and the path as: /Users/{my user name}/Dropbox/.dropbox.cache/~f90{blah blah blah}.tmp

Appreciate any help on this. thanks

try clear your dropbox cache

https://www.dropbox.com/help/328
http://www.dropboxwiki.com/forums-faq/clear-dropbox-cache

appreciate the response but once the cache rebuilt itself, the alerts started appearing again.

None of the paths mentioned here exist in my computer… Windows 8.1 x64