Naive use of spelling-checkers can quickly lead to garbage, and/or a combinatorial explosion. To paraphrase J sinclair -- it is wrong to consider spelling without also considering the lexical and syntactic context in which the spelling error is made.
Speaking from experience, I've found that running text through a spell-checker before doing any other processing mostly just damages the text. The best strategy seems to be to leave the mis-spelled word in place -- and add it to your NLP or machine-translation lexicon, which will "understand" enough of the syntactic/lexical environment to "do the right thing" with the mis-spelled word.
--linas