Two recommendations for you:
1. Use mysysprep (http://www.tsaysoft.com/mysysprep2/
) As you can see from the site, it supports many more features than the MS version. I have used it for years without a hitch.
2. If you insist on using the MS version, store your sysprep answer file in "C:\Windows\Panther". Overwrite the one that's in there if there is one and be sure to name it "unattend.xml". Then point sysprep to that. I had an issue with my answer file not being found when sysprepping a VM from Virtual PC and this resolved the issue.
If possible, upload a copy of your unattend and I can look through it for you, please remove any sensitive data (i.e. passwords) before uploading. Also, please provide more insight into your image; is it of a physical machine or VM? what software is on the image? etc.
Also, if these machines will be joined to a domain I wouldn't try re-imaging without a sysprep. I have experimented with that in the past on identical hardware and it has lead to instability and licensing issues that could only be solved with a fresh installation. My advice is to spare yourself that headache.
I look forward to helping!