BookCAT is a (still) extremely popular piece of library software. The internet searches are fully functional when I kill avast, but with Avast running there is contact with the search sites, like Amazon, library of congress and so on. You can see the byte count being downloaded. But all internal handling of the data is dead.
Avast gave the same kind of problem with a mysql manager a long time ago, and the actual fault was never found. However, the fault disappeared after a year or so.
I use the free avast, mainly because of the small footprint.
