PTGO:
Much depends on your annual income and filing status.
If you are single or head of household and your income is below $45K, you can open a traditional IRA even though you have a 401K, with reductions for amounts over $45K to $55K.
If you are married or a qualifying widow(er) and your income is below $65K, you can open a traditional IRA even though you have a 401K, with reductions for amounts over $65K to $75K.
You also have the option of opening a ROTH IRA, which has much higher cutoffs ($150K - 160K for married) and which, In my opinion, is a much better deal in the long run.
Full details can be found in IRS Pub 590 which can be download from
www.irs.gov.