Optistruct ERROR 155

I am having the same eeror message.

I am just doing few experiment with RADIOSS for a few linear modal models.

This is the error message:

A fatal error has occurred during computations:

*** ERROR # 155 ***

Three numerical factorization in a row failed. Probable cause

is that there is a massless mechanism in the model.

Solver error no. = -729

subcase id = 3

Check the model and rerun the problem.

(MECHCHECK may be used to check for massless rigid body modes.)

(WARNING: results obtained with MECHCHECK cannot be used because

the model is changed internally.)

...

I have deleted the MPC parts in my model and now it is running.

What it is wrong with my MPCs? Model check was saying that they were OK????

Any help?

I have the exact same error and don't know where its coming from. The model was running perfectly and I remeshed and it create this error! I have no where it comes from. 

do you have solve this problem?  i have the same problem !

Check the element type and load type for the subcase. That might help is solving the problem

If you are doing modal analysis (free free run) then increase Value of V₂ and number of modes to be extracted and see the error goes off.

Helloo

I am having the same problem, although I increased the value of V2 and number of modes to be extracted
Any other way to resolve ??