[Mono-list] Requests get stuck with mod_mono

[Mat Efha]

Hello!

I am developing a RESTful web service using the ServiceStack framework and I
deploy it using Apache and mod_mono.

My problem is, that a lot of requests appear to get stuck somewhere in between
apache and the mod-mono-server. I activated the mod_mono control panel and I see
an ever growing list of requests there, which never get processed:

myservice

    Restart Server
    Stop Accepting Requests
    148 requests currently being processed; limit: 150; total: 3660

        1363 661s /myservice/users/3606/items/4
        247 945s /myservice/items/2/data
        2350 424s /myservice/items/4/data
        1237 692s /myservice/items/3/data
        ....

Most requests do get processed, but the list with the dead requests is always
growing until I restart apache or mod-mono-server. It is not a hardware issue.
The CPU is rather bored (load usually around 2 on a quad core), I have enough
RAM available and never need any swap space.

Does someone have an idea, what might cause this?

regards
Mat