IMMEDIATELY AFTER he took office as governor of Maryland, Harry Hughes did something that most politicians wouldn't think of trying right off the bat: he raised a generally unpopular subject -- prisons -- and then picked a controversial corrections cheif to make policy changes that were bound to be initially misunderstood in the General Assembly. The idea was move the state away from a simplistic and unsuccessful lock-'em-all-up-in-big-prisons approach to corrections and to comply with court-ordered deadlines for ending overcrowding. Now, after extraordinary success in winning general agreement on some forward-looking policies, the governor's corrections efforts have run into new difficulties -- not political, but logistic.

The trouble? Window frames. Late delivery of special window frams means that a new 400-bed prison under construction in Baltimore won't be built in time. This facility is an important part of a balance between building more big prisons and speeding up parole procedures to release more non-dangerous inmates. It was to open this year, in time to absorb more than 300 beds that are supposed to be eliminated at the Maryland Correctional Institution in Hagerstown by Jan. 1.

The governor's corrections chief, Gordon C. Kamka, says he hopes to continue the accelerated parole program. This program has been working reasonably well so far; one year after 400 inmates were given early releases, 9 percent have been returned to state prisons after convictions for new crimes (though others eithe have not been tried or have violated parole conditions). But the program was not intended to be -- and should not be -- stretched to cover the latest construction delays. The object has been to release non-dangerous prisoners only if parole standards can be mantained. That takes people to cover the increased work, but it is essential both for society's sake and for the welfare of those inmates involved.

If construction deadlines can't be met, the administration should seek an extension of the Jan. 1 deadline. This will surely bring howls of protest from hardliners' opposite numbers, the all-prisons-are-bad-school. But in any state or local system, until there is agreement on, and construction of, more sophisticated community facilities, a prudent balance of new prisons and careful release procedures is the only sound approach.