Error in twInterfaceObj$doAPICall(cmd, params, method, ...)

[iPALVIKAS]

I am requesting multiple time a userTimeLine and creating a list of details like tweet time, URL , location etc.
But here in my case, the twitter connection is authorised and sometimes during the execution of the code I get this error

---

Error in twInterfaceObj$doAPICall(cmd, params, method, ...) :
OAuth authentication error:
This most likely means that you have incorrectly called setup_twitter_oauth()'

---

I am not able to understand the cause of this error. Please help me in this.
Thank you.