Texas is one of the states with an Oridinance of Secession that mentions the Northern states attempt to abandon the Constitution and interfere with slavery. There is much more. Here is another cause:

"The Federal Government, while but partially under the control of these our unnatural and sectional enemies, has for years almost entirely failed to protect the lives and property of the people of Texas against the Indian savages on our border, and more recently against the murderous forays of banditti from the neighboring territory of Mexico; and when our State government has expended large amounts for such purpose, the Federal Government has refused reimbursement therefor, thus rendering our condition more insecure and harassing than it was during the existence of the Republic of Texas."

http://www.lsjunction.com/docs/secesson.htm