I’ve experienced this here as well (2.53 gHz MBP, 4G Ram, Metric Halo ULN8).
In addition to the issues reported, I’ve found that when re-opening sessions with an External Gear ASIO plug in the master section, that plug is never saved. It’s always an empty slot. I just put it into a saved chain, so it’s easy enough to recall now, but still… bug.
It may be a fluke, but for some reason my rig’s renders with External Gear are more reliable when I monitor the render path as it runs down. I can do this via MIO Console, even though WL7 keeps the task itself in the background. In that configuration I get less dropouts.
The problem is bad enough and consistent enough that I’ve mostly stopped rendering entirely, and just playback out of WL7 and capture manually in MIO Console. It’s more reliable as a recorder, and ensures I see/hear errors as they happen. Given Philippe’s comments I think I’ll stick to this approach, and avoid External Gear plug entirely.
As cool as it seems and feels, I’m not convinced any process involving External Gear should EVER be a background task, at least on macs (PC MMV). I see few functional benefits to pro mastering engineers for “rendering” captures as background tasks. I concede this feature may be slick and compelling to DIYers, newbies and non-pro users, but given the nature of mastering gear (unique, expensive, hand-patched and modded), once it’s engaged in a delivery, you can’t really do anything else anyway. Further, if you want to change settings or something, you’ll need to hear what’s going on. So in most applications, foreground capture (already possible, maybe more stable already) is most desirable. I guess if all you’re doing is limiting or curving something you might like background, but it’s really a nice-to-have feature, not an ideal.