I have not heard anyone having this issue...

You may try opening the program from Xterm and see if it gives any error message... (I do not know what the command is? Modest? Someone with tablet in hand maybe can check...)

Second try might be to reset Modest settings... which likely can be done by deleting .Modest directory... (Sorry I do not know the path... and can't check because I do not have the tablet with me at the moment.)