BroMac:
The Bible Knowledge Commentary (OT p.1161) has this to say about Jeremiah 25:12:
"After the 70 years were fulfilled God would also punish . . . the Babylonians because of the guilt they had incurred. He would fulfill all the things . . . written in Jeremiah's book against Babylon. The material to which God alluded is in chapters 50-51. Evidently at least part of chapters 50-51 was written about the same time as chapter 25. God would repay Babylon according to her deeds."
Note that the ellipsis and bolding of the text is from the publication itself. The bold text corresponds with the wording of the NIV Bible.
Based on the commentary above, chapters 50 and 51 should offer some clues as to Babylon's "error" (NWT), "iniquity" (YLT, RV, KJV, JPS, ESV, Darby, ASV), "evil-doing" (BBE), "sins" (ERV), "crimes" (GW). The Hebrew word translated "error" is awon. The AMG Hebrew dictionary defines it as "sin that is particularly evil, since it strongly conveys the idea of twisting or perverting deliberately. The noun carries along with it the idea of guilt from conscious wrongdoing. (Gen 44:16; Jer 2:22)"
(There is a good bit more in the definition, but this part seems most applicable to Jer 25:12.)
Hope this helps some.
Take Care