Those who thought that the Dell buyout was done and dusted might need to think again. Apparently, some of the PC maker’s major shareholders – the very people who have the power to put the skids on the deal – are none too pleased about CEO Michael Dell’s valuation of the company.

We first heard rumblings of discontent late last week, when it was revealed that Southeastern Asset Management, the single largest investor in Dell, was “disturbed” by what it perceives to be a massive undervaluing of the company.

Now it seems that the second-largest investor in Dell is echoing these concerns. Earlier today, the T. Rowe Price Group announced that it would not accept the $13.65 per share offer proposed by Michael Dell, according to a report by Bloomberg.

Brian Rogers, Chairman of T. Rowe Price, basically told Bloomberg in an email that he believed the investors were being screwed over:

“We believe the proposed buyout does not reflect the value of Dell and we do not intend to support the offer as put forward,” writes Rogers.

Reading between the lines, it’s obvious that the major shareholders are holding out for more money, and in order for Dell’s buyout to go ahead the company is going to have to do something to sweeten the deal. Most likely Dell will still end up going private, but Michael Dell will need to find a way to stump up more pennies for its investors before it can do so.

As well as Southeastern Asset Management and T. Rowe, which together hold about 12.8% of Dell’s shares, a third investor has also indicated that it does not agree with the proposed price. Pzena Investment Management, which holds 0.7% of Dell shares, also piped up with a dissenting voice today, which means that those opposed to the deal now have the required minimum of six investors holding over 18% of the company to be able to block the takeover.

Michael Dell, who currently controls 14% of the company, appears to be desperate for the deal to go through so that he can press ahead with his plans to restructure Dell as an enterprise software supplier away from the watchful gaze of shareholders.  What with things having progressed this far already, it’s hard to see the wheels falling off the deal now, although there’s bound to be plenty of hard negotiating going on behind the scenes as the entrepreneur is unlikely to meet the $20 per share valuation that some investors have reportedly put on the company.