Story highlights A Massachusetts woman says an iPad she bought from Walmart was fake

A rash of similar cases have been reported in the past six months

Walmart is aware of the problem and is working to address it

Advice: Open the box in the store and check the serial number on the box as well

But when you're like Suzanne Nassise and you buy Apple's popular tablet from a well-known retailer, you expect it to be legit. Nassise says she walked out of a Walmart in Brockton, Massachusetts, last month with what she believed was a new $499 iPad.

When she got home and opened the box, she told CNN affiliate WCVB , she thought, "'Wow, it's a little on the light side -- Apple's an elegant product.'"

Then she tried to turn it on.

When nothing happened, Nassise looked at the plastic rectangle more closely. The imitation iPad -- an iFake, if you will -- tried to replicate a real iPad's charging port and speakers, the latter of which were small, painted-on dots.

"When I realized it, I was upset," she told WCVB. "I just paid $500 for a paperweight."

Susan Nassise paid $499 for an iPad at a Walmart in Brockton, Massachusetts, only to open the box and find a plastic fake.

If her story sounds familiar, it's because it has happened at retailers in a variety of states over the past few years. Numerous shoppers have purchased what they thought were iPads, only to open the box and find a worthless decoy inside. To make matters worse, some stores have refused to give refunds on the grounds that the buyers might have been trying to scam them.

The majority of news reports on the problem have involved iPad purchases at Walmart, although other retailers are not immune.

The next year, Ken Lemal told a similar story after the businessman purchased what he thought was an iPad from a Walmart in Woodstock, Georgia. Like Nassise, Lemal's iPad was packaged in a way that suggested he was buying a product straight from the manufacturer.

"I think that probably somebody switched (the iPad) and took it back with the cellophane and everything," Lemal told CNN in a recent interview. "An employee says, 'Oh it's wrapped up, we'll stick it back in inventory,' and it gets sold to somebody else. I think that's what happens."

In January, a woman in Randolph, New Jersey, said that she, too, wound up with a fake Apple tablet after shopping at her neighborhood Walmart.

"When I got home and opened the box, I thought it was a real iPad," Jamie Frick told the Newark Star-Ledger. "I took out the charger and then tried to plug it in the iPad, and that is when I started to notice everything."

So how is this fraud happening? Retail chains aren't saying. But the prevailing theory begins with a scam artist buying an iPad, replacing it with something of similar size and weight and then repackaging the box so it looks ready for the sales floor once again. Then the person returns the box for a refund. Other speculation has focused on unscrupulous store employees raiding storerooms to make similar swaps.

Walmart at first declined to offer Nassise, the Massachusetts woman, an exchange or refund because of a policy against returned merchandise that has been unwrapped. But after the local ABC station got involved, Nassise eventually received a refund for her purchase.

Walmart spokesperson Dianna Gee said the company is aware of the problem and is working to address it.

"We're actively reviewing our transactional records, and then going back and looking at the video that matches up with that to determine how this product is getting back on our shelves," she said. "If it appears that it is fraudulent, we will share all that information with local law enforcement."

Best Buy, which has seen similar fake-iPad episodes, did not respond to repeated requests for comment.

Walmart's Gee recommends that iPad shoppers open the box and check the tablet carefully before making a purchase.

Lemal's experience made him wary of purchasing items from anyone other than the manufacturer. But he did learn a valuable lesson: Double-check the serial number on the box.

"If you have an issue, don't rely on the retailer to just check the item that's inside the box; call Apple and verify the serial number that's on the box itself," he said. "Either require them to do it while there, or when you get home ... (that will tell you) if it had been sold prior to your date of purchase."