At first sight, given its location (a .dll file in temp) and random looking name, I would say avast is right to be suspicious of it. So for now (until further investigation) I would say not to Add the file to the scan exclusion list or Report the file as a false positive.
This needs further analysis by a malware removal specialist:
Go to this topic
http://forum.avast.com/index.php?topic=53253.0 for information on Logs to assist in cleaning malware.
Use the information about getting and using the tools and attach the logs here, not in the LOGS topic.
Since you have already run MBAM, you could attach its scan log to your next post.
Start with the Farbar Recovery Scan Tool (second one on the above link) and attach the two logs mentioned in the Information topic I gave the link for.