Hi Janos,
If those DWH files are only appearing the the Temp directory, then it's most likely that you are seeing a product issue rather than an infection. The following articles contain additional information.
When new virus definitions are in place and the quarantine is being scanned, a DWH file is created and detected by Auto-Protect
Article: TECH102953 | Created: 2007-01-19 | Updated: 2012-02-09 |
Article URL http://www.symantec.com/docs/TECH102953
Defwatch temp files are re-detected in temp folder
Article: TECH138856 | Created: 2010-08-31 | Updated: 2011-01-22 |
Article URL http://www.symantec.com/docs/TECH138856
DWH***.tmp files are detected in the user profile temp directory.
Article: TECH92399 | Created: 2009-01-16 | Updated: 2012-02-06 |
Article URL http://www.symantec.com/docs/TECH92399
Updating to the latest available SEP will resolve several of the underlying causes and reduce the number of DWH "detections."
Please do update this thread to confirm if this matches what you are seeing!