First thing's first: get ahold of the SPD (Summary Plan Document) - that will tell you what events can trigger Distribution. Typical triggers include:

Death (not recommended for most Client);

Disability (also not recommended, but not as bad as the previous option);

Attaining age 59 1/2 (even if still employed with the current employer);

Severance from employment (but you already knew that one);

Termination of the Plan (but only if there is no appropriate Successor Plan);

Military Service for a Qualified Reservist (details need to be understood), and;

Hardship (no guarantee that this is in the Plan).

Please note that Hardship Distributions cannot be Directly Rolled-over into an IRA. An indirect Rollover (with 20-30% withheld for Taxes, in most cases) would be the most commonly available option.

Note: http://www.irs.gov/retirement/participant/article/ 0,,id=151787,00.html is a good start for Distributions from Retirement Plans (if you haven't read it already).

Do you still have questions? Try contacting a firm that has an ERPA-designated individual (or someone with similar experience/knowledge and relative independence from a TPA) to go over what your particular Client's options are for her/his particular employer's Plan.

Good Luck and Good Speed!