what can I do mabout them
upload the file to avast lab so that they can correct the detection

You can report a possible FP here: http://www.avast.com/contact-form.php
you may add a link to this topic in case they reply

you can also use mail

send to virus@avast.com in a password protected zip file
mail subject: false positive
zip password: infected

or you can send files from avast chest
how to use the chest. http://www.avast.com/faq.php?article=AVKB21

you can also upload and test the file at www.virustotal.com and see if others detect it