The White House says it's just a misunderstanding, and Karen Carlin, whose husband John is the governor of Kansas and chairman of the National Governors' Association, seems to agree.

The misunderstanding comes over whether Karen Carlin should have been seated at President Reagan's table at Sunday night's dinner for the governors and their spouses. For the record, she wasn't and isn't sure why.

Could it be that the White House is afraid of the fact that she's an antinuclear activist who tried to get a Pentagon tour and briefing from Robert McFarlane, Reagan's national security adviser, for the governors' spouses who are in town for the winter meeting of the NGA?

"It's no big deal," said her husband John.

Karen Carlin didn't get the administration to give the governors' spouses a Pentagon tour or the briefing from McFarlane.

On Sunday night, she sat with Vice President Bush. "I had an enjoyable evening with the vice president," she said yesterday. "He's a very charming man."

"I'm not making anything of it at all," said her husband John. "I sat with the first lady and had a delightful evening."

Some governors believe the custom at such White House dinners is for the NGA chairman to sit with the first lady and the spouse of the chairman to sit with the president. On Sunday, Honey Alexander, the wife of Tennessee Gov. Lamar Alexander, a Republican, sat with the president.

Jennefer Hirshberg, Mrs. Reagan's press secretary, said Honey Alexander drew the seat with Reagan because her husband is NGA vice chairman and for some years the White House has tried to "honor" both the NGA chairman and vice chairman in their seating arrangements.

"Except last year, I didn't sit with the president," Karen Carlin said yesterday.

That was when her husband was NGA vice chairman.

Last year she sat with McFarlane and found him quite interesting, which is why she hoped to have him speak to the governors' spouses as a counterpoint to a session they had with scientist Carl Sagan. The administration offered a tour of the State Department and threw in a talk from Paul Nitze, Secretary of State George Shultz's special adviser on arms control.

"He's Mr. Arms Control," Hirshberg said. "They couldn't do better."

"I'd have much rather had the opportunity to go to the Pentagon," Karen Carlin said.

Carlin is a member of Peace Links, a nonpartisan organization of women against nuclear war. She also said she spent a lot of time on the set of the movie "The Day After," which depicted a nuclear attack on Kansas. She thought a Pentagon tour and briefing from McFarlane would add some substance to the agenda of the governors' spouses.

She was described yesterday as "5 foot, 1 inch of dynamite."

"I'm 4 feet 11," she said, joking she was excluded from the president's table because she was "too short."

Her husband was asked if he thought the administration knew about her connection with Peace Links. "I imagine they know of her," he replied.