Application to adjust status form I-485
It would appear for whatever reason they believe they may have made a mistake in issuing your residency.
While you can theoretically travel, if they decide to revoke your status while you are outside the U.S., you will have trouble coming back into the U.S. You should focus your efforts at this time on responding to any notice they give you as to why their initial decision was the correct decision.
Brian D. Lerner
Attorney at Law