Recent ERP studies report that implausible verb-argument combinations can elicit a centro-parietal P600 effect (e.g., "The hearty meal was devouring..."; Kim & Osterhout, 2005). Such eliciting conditions do not involve outright syntactic anomaly, deviating from previous reports of P600. Kim and Osterhout (2005) attributed such P600 effects to structural reprocessing that occurs when syntactic cues fail to support a semantically attractive interpretation ("meal" as the Agent of "devouring") and the syntactic cues are overwhelmed; the sentence is therefore perceived as syntactically ill-formed. The current study replicated such findings and also found that altering the syntactic cues in such situations of syntax-semantics conflict (e.g., "The hearty meal would devour...") affects the conflict's outcome. P600s were eliminated when sentences contained syntactic cues that required multiple morphosyntactic steps to "repair". These sentences elicited a broad, left-anterior negativity at 300-600 ms (LAN). We interpret the reduction in P600 amplitude in terms of "resistance" of syntactic cues to reprocessing. We speculate that the LAN may be generated by difficulty retrieving an analysis that satisfies both syntactic and semantic cues, which results when syntactic cues are strong enough to resist opposing semantic cues. This pattern of effects is consistent with partially independent but highly interactive syntactic and semantic processing streams, which often operate collaboratively but can compete for influence over interpretation. (Contains 3 figures.)