That sounds familiar also. I was close to 30, but not really at 30 when counting the requests.

Basically support said that my application API limit was also set to 30 rather than 60 for some reason. So they increased it to 60, and after that I've not had any problems.

To be honest I find the FAQ a bit confusing on the limits, specifically
Per-app non-trading requests per minute: 60
Per-account non-trading requests per minute: 30

To me it seems like the per-account limit of 30 would always be hit before the per-app limit, since all app keys belongs to an account.
I've sent a mail to support asking them to clarify this as well, I'll post back here when I get an answer.