Shouldn't be a problem, but...... if you plan to come back to Cyprus (not Cypress), you may have a problem as there will be no record of you leaving the RoC (I do not believe that the TRNC exchanges immigration data with the RoC). Your passport is not stamped when leaving the RoC to go to the TRNC and vice versa. Also, when you go through immigration at ECN, if the immigration officer is perplexed about you not having a TRNC entrance stamp in your passport, just tell him which crossing you came through to the TRNC - he will then be able to find you in the computer.
Also, recently RoC immigration is interested in people flying into LCA and then going to the TRNC to stay. It has to do with staying in "illegal" TRNC hotels (hotels on Greek Cypriot land taken by the Turks during the 1974 invasion), so keep your intentions to go to the TRNC to yourself when going through immigration at LCA.
I last crossed the green line in December. My residency permit was scrutinized upon re-entry to the RoC (have a Cyprus permanent resident permit in a US passport).