PS generate Invoices and Shipping list with .exe extension

[TassaDarK]

Hi, i have a VERY weird problem with my shop. I didn't have any problem until now with automatic generated invoices and shipping list from BO and from user's "my orders" section but today i was downloading some shipping list of orders and found out that PS is generating the documents with .exe extension in place of .pdf

The thing is, if i rename manually the file to .pdf it works fine, but this is very weird.

Any ideas? Where is can i see the php code to correct this? Is it possible i have been victim of a hack attack and they modified my php files to insert trojans and viruses? how can i investigate this? i'm a bit scared :-(

Thanks in advance

PS: ups! this only happens with opera browser, all is fine with IE and Firefox.