Invalid Function pointer error

[Kiran C]

Hi,
    I have a strange problem using RTEMS.I have  implemented a linked list
Timer.
    ie.A timer list is maintained.every time I call rtems_clock_get ..
    get the time diffrence ..ie the elapsed time..and I call the callback
function for the timer(ie the software timer I implemented).
    The above mentioned code works  well..but as time passes ..say almost
after 26 sec
    I get the follwing error in the psim
--------------------------------------------------
cpu 1, cia 0xfff00700: double interrupt - MSR[RI] bit clear when attempting
to deliver interrupt, cia=0xfff00700, msr=0x1040; srr0=0x0(cia),
srr1=0x8b042(msr); trap-vector=0x700, trap-msr=0x1040
./o-optimize/tca.exe: Caught signal -1 at address 0xfff00700
----------------------------------------------------
I tried debuggung this..what I found was that the callback function pointer
is now 0x0.
But earlier it had a valid pointer..and the call back function was
called.What could be wrong?
I tried running the same code in pc386 ,then I came across ,Exception
13,What does that mean.(I was running it in VMWare)
But it ran longer than in psim.
Has it got any thing to do with how much RAM ,STACK SIZE et al is allocated
for each task?
Hoe you can help me..
Kiran