Just bought 3 new U2415's for their daisy chaining capability.  When I connect them as per directions, they do indeed daisy chain, but almost immediately they begin blinking to black screen and on again, like lights on a Christmas tree (only slower). 

My setup:
Mobo:  Asus P8P67
GPU:  Radeon HD 6850
SSD:  Samsung 850

At first, all I could get the monitors to do was mirror each other. 3 expensive monitors showing the same thing doesn't work for me.  After 3 hours with Dell phone support they finally told me no mas without solving the issue, because the monitors were not connected to a Dell PC.  Disappointing.

So, I disconnected all my drives except the SSD and did a fresh Windows 7 install from DVD, and then downloaded and installed all of the Windows updates. Installed Dell monitor driver off of DVD that came with monitors. Updated Bios and latest chipset, GPU drivers and AMD Catalyst Control.  Nothing else is on the SSD besides Win 7, Windows Security Essentials, Malwarebytes. No other storage drives.

I reset all of the monitors to factory settings and then Enabled DP1.2 on the monitors #1 & #2.  Monitor #3 was already Disabled.  Voila...Windows recognized 3 independent monitors and I was very happy. Until they started to blink on and off after a few minutes.  The AMD Radeon HD 6850 specs claim to support:

• DisplayPort 1.2
• Max resolution: 2560x1600 per display
• Multi-Stream Transport
• 21.6 Gbps bandwidth
• High bit-rate audio

My monitor cables are DP1.2 and brand new. Windows is fresh, bios and drivers are up to date. This is driving me crazy.

So, anyone have some ideas on what I am doing wrong? Is there a super secret Dell pay support line that I can call? I am willing to pay, provided I get this solved.

Thanks!