I've been developing an app using the Magento REST API, and up until now, its all been going fine. However I've run into a problem when I try to add data to the db.

Here's my error message:
oauth_problem=signature_invalid&debug_sbs=hb5S\/USOyhh1XgWSLp3RzTCNvgE=

Here's the authorisation sent with the request:
OAuth oauth_consumer_key="xxxx",oauth_signature_method="HMAC-SHA1",oauth_nonce="40713647551fa3cde5da131.80878000",oauth_timestamp="1375354078",oauth_version="1.0",oauth_token="xxxx",oauth_signature="Oc6EgugEcZu2fPtcy9VEROFExzI%3D"

I have no idea how to debug this issue.

Its been recommended that I install xdebug into Sublime Text, which I've done, but I'm not really sure how to use it :s... I've tried debugging the script, but nothing seems to be coming back.

Does anyone know how I'd go about debugging this?

Best,
Mike