I have been developing applications based on C# (.net) and Java (J2EE) for the last 3 years.
But now I feel, Java, C# makes you lame (from learning point of view) and yo
C and C++ make some basic underlying programming concepts more evident, but they weren't designed by God. I'd second the suggestion to study the actual low-level systems behind your low-level code: operating systems, compilers/runtimes (try "Essentials of Programming Languages"), and machine architecture.
P.S. In general it may be better to study C++ on its own, rather than starting with C, but for your particular purpose -- getting more intimate with low-level, unsafe constructs such as pointers, after already learning Java -- I think it's better to start with C (and K&R) where these are front and center.