Anti-Virus Alerts on Tbird Portable

All of a sudden, after years of use, with no alerts, I am getting anti-virus alerts on my work computer when I start/use Thunderbird portable. I would like to post a printscreen, but don't see how to do it. I also can't test the detected item because McAfee deleted it. But from the log there is this:

rheath ran H:\PortableApps\ThunderbirdPortable\App\Thunderbird\thunderbird.exe, which attempted to access H:\PortableApps\ThunderbirdPortable\Data\profile\startupCache\startupCache.4.little\contentAreaClick.js. The potentially unwanted program named Suspicious Attachment!script was detected and deleted.

There were 51 "threats" and all of them were similar and in the startup cache. I deleted all the history and cache, so at the moment this folder is empty.

Can anyone advise? Was this a false threat, or should I be concerned?

Thanks.