Need help from analog gurus. 78L08 output at -0,9V

[dmg]

I have a problem with a prototype circuit I had to rush in a week. It pretends to be a dual channel very high quality audio DAC with some requirements for distortion, flatness and bandwidth. I based it on the PCM1794A (http://www.ti.com/lit/ds/symlink/pcm1794.pdf) from Texas Instruments using a slight variation of the proposed output buffering circuit in the datasheet page 20(uses LT1028 as differential amp and a couple of NE5534 as IV converters for each output).

We use a triple channel switchmode PSU (that switches at 110 kHz) to power the whole system (it must fit in a 1U rack case and height is too constrained for a linear PSU) with +5V, +12V and -12V rails. In the DAC board the +-12V rails are LC filtered and post-regulated using 78L08 and 79L08 regulators to the +-8V that feed the opamps of the oputput stage. They're decoupled using ceramic caps (and i'm aware it might be part of the problem). The 78L08 is TI branded (ua78l08) and the other is MCC branded

The problem comes when we power up the board. The -8V rail gets to -8V without any problem but the +8V one goes to -0,9V and stays there. Then, if you unplug the -12V rail the +8V rail goes up to spec and stays there. Then if you re-plug it the -8V rail goes up and both rails stay up and the thing runs until you power the board off. We've red-necked the issue adding a delay switch in the -12V rail so it only powers the board once +8V are present but this must be turned into a commercial product in about a month and I'd rather solve the issue than patch it.

Any clues about what may be happening? Something should be pulling the +8V rail negative until it reverse-biases a transistor in there preventing regulator startup, hence suspiciously staying at -0,9V, but I don't know how to solve the issue right now and i'm a little intoxicated with soldering fumes to think. Any clues?

[wraper]

Likely, during power up 78L08 output gets pulled below zero and IC stops work correctly. Add reverse voltage protection diode like on the picture.

[dmg]

Bingo, thank you very much.