Has there any mutations been recorded which cause harmful effects due to change in the part of pre-mRNA responsible for proper m-RNA splicing ?
Yes, you can find mutations in the genomic DNA which affect splice acceptor sites. Wikipedia lists the following outcome:
The article lists two interesting papers:
Lim KH, Ferraris L, Filloux ME, Raphael BJ, Fairbrother WG (2011). "Using positional distribution to identify splicing elements and predict pre-mRNA processing defects in human genes". Proc. Natl. Acad. Sci. U.S.A. 108 (27) 11093–11098.
Ward AJ, Cooper TA (2010). "The pathobiology of splicing". J. Pathol. 220 (2) 152–163.
Both papers are open access.