I'm not sure why or even how you got video off a DVD as WMVs, but that would definitely not be the smart way to go.
Instead, put the DVD in your disc drive and use Premiere Elements' Get Media/From DVD Camcorder or PC DVD Drive to rip the files to Premiere Elements. (Make sure your project is set up for Hard Disk Camcorder first though, or you'll end up with an interlacing issue!) Once the program conforms the video files, you should be able to edit them as if they were your original video files.
Converting to WMV first actually takes you farther from where you want to be.
BTW, what do you mean by "I removed it from the disc it was originally burned to in iMovie"? Do you still have the original video files? What format are they in and where did they come from?
You're always better off getting closer to the original source than using files that have already been through one video editing program and burned to DVD.
I agree with Steve on his suggestions.
The original files will be the best source, but if all you have is a DVD-Video, then Importing the VOB's would be second best. This article goes into more details on DVD's and VOB's: http://forums.adobe.com/thread/464549?tstart=30
If your DVD-Video was authored as 100% DVD-compliant, then you should have not issues. If, however, it was authored with either hardware, or software, that did not create 100% DVD-compliant VOB's, then you will likely have issues, and especially with the first VOB.
As for WMV, it is a delivery-only format, and is not well-suited for editing. PrE CAN Import WMV's, but that is not the ideal workflow for several reasons. First, you have material, that was compressed and Encoded to MPEG-2 DVD. Then, with WMV, you are compressing again. Also, the processing of the WMV takes a lot of power, just for simple operations.