When I upgraded from BDIS 2008 to 2009 late last year, I lost the ability to view the scan logs. This apparently is caused by some sort of conflict with the logs and Window's Data Execution Prevention feature. BitDefender's remedy is the standard uninstall and reinistall, which gave the standard result of nothing. One link on the internet had a comment in some context not necessarily tied to this suggesting the offending programs need to be made Data Execution Prevention friendly.
I did find a workaround today. If you can find the log file, you can right click on it and choose the "Open with" option (Notice this is different from the "Open" option) and choose to open it in Notepad. You may have to dig a bit to find Notepad. This will open the log in text format and while a bit cryptic, you can get most of the information from it.
On my computer, running XP, the log files are found by going to the Control Panel, Folder Options, View, and making sure the box next to "View hidden files and folders" is checked (remember to undo any changes when you are done), then using Explorer (Windows key +e) find the following folder:
C:\Documents and Settings\All Users\Application Data\BitDefender\Desktop\Profiles\Logs
In that folder will be a folder for each type of scan, such as "deep_scan" so open the relevant folder and you will find the scan logs, such as 1241370557_1_02.xml
Interestingly, using XP's Find feature and searching for *.xml will not find these files so if the scan logs are not as I have shown above, they may be tricky to find. Probably the interent or this forum can help find where they are hidden. I don't know if BitDefender Customer Service would know where they are.