Thank you for posting in Wired Communities. I have branch out your post so that we can further discuss from here. Can you share more information about your setup:
1) What is the exact model of the NIC? Is it also an 82574L?
2) What is the the server model?
3) What is the operating system used?
4) What is the driver version?
Other relevant information you can provide would be better for us to further check.
Thank you for sharing the update and solution, I am glad the issue is resolved. Please feel free to contact us if you have other inquiries.