This post May Not apply to you but I hope it helps.
I have had some people that have reported issues connecting to a share with Mount Manager on a 4.2 device.
First, make sure you have the required modules for your kernel. This post will be using CyanogenMod 10.1 as the reference, but your ROM may differ and YMMV.
In CM10.1 you have to load 3 modules to get cifs to work correctly. cifs.ko depends upon dns_resolver and md4 modules. They have to be loaded before cifs.ko.
Once you have these modules loaded you should be able to mount your shares. If you are still having issues try looking at this post on XDA. It seems there is an issue with some builds of busybox that it needs the unc option added to the connection.
You can add a new option when creating a mount point and select custom. Then enter “unc” as the name. For the value you will enter the same path that you use for the network share, except you have to use “\” instead of “/”. And you have to escape them. So you need to use 2 of them for every one you enter.