Building up messages as a cognitive activity within the linguistic multi-level system is the result of the interaction between the various components of this system. Yet, this interactive process occurring in the language user's mind while encoding can vary from person to person. Likewise, it also differs in different recipients while decoding. This cognitively carried out difference in encoding can result in either unintended messages, though emptied out in mature and well-formed language constructions, or ill-formed ones. The present study aims at identifying the most frequent syntactic errors at the sentential level; and how immature or vague conceptualization manifests itself in the grammar-meaning relationship as reflected in the subjects' errors. Data were collected from the writings and the performance tests of mainly two Arab groups of third and fourth-year English majors in the course of Sociolinguistics at the University of Nizwa in the Sultanate of Oman. Errors were identified, classified and interpreted in terms of the underlying cognitive processes they went through during production. Errors were related to time-tense vague mapping, finite-nonfinite confusion, sentence-clause uncertainty, incorrect embedding, voice-related inaccuracy and verbless clauses or sentences. ********** Errors in second language performance are easy to observe, and undoubtedly serve as good indicators of a learner's level of second-language knowledge. Thus, they are an integral component of language learning. The phenomenon of error has received the interest of researchers, though traditionally has been regarded as the linguistic phenomena deviant from the language rules and standard usages, reflecting learners' deficiency in language competence. Hence, many teachers simply correct individual errors as they occur, giving little concern to identifying patterns of errors or to uncovering causes other than learner ignorance. However, interpreting what the cause of these errors has been a major concern for linguists, as well as classroom practitioners. In this respect, Steinberg and Sciarini (2006), state that the systematicity of most errors is the result of the application of certain strategies when relevant second-language knowledge is not available or incomplete. Conscious resort to any of these strategies is definitely a cognitive exercise, the results of which are various deviations of the linguistic norms, sentence patterns and rules that put the language components together to produce linguistic moulds embodying composites of thoughts. Presently, therefore, with the development of linguistics, applied linguistics, psychology and other relevant subjects, attitudes toward errors changed greatly. Instead of being problems to be overcome, errors are viewed as an evidence of the learners' stages in their target language (TL) development. It is through analyzing learner errors that errors are elevated from the status of undesirability to that of a guide to the inner working of the language learning process, as (Ellis, 1985, cited by Nassaji & Fotos, 2004, at http://faculty.ksu.edu.sa/dinaalsibai/ReviewGrammar.PDF) puts it. The term grammar is used in this paper to include the two language levels of syntax and morphology since some errors in one level cannot be explained in isolation from the other. For example, the past tense of bring is brought, a case of inflection under morphology, whereas the interrogative form Did bring them? of Ali brought them is a syntactic issue. Memory and logic, which are cognitive skills, play a crucial role in language learning. As Steinberg and Sciarini (2006: 34-35) state it, that while learning to identify the words of the language, formulating rules for their use, and relating speech to the environment and mind, the child employs an exceptional memory capacity. In this respect, a massive number of particular words, phrases and sentences have to be remembered in connection with the context, whether physical or mental, in which they took place. …