Same data for different key in table takes lots of time

Question

I have a table...

FactorID, col1 col2     Factor Value
1         a     2        1231
1         b     3        2342
2         a     2        1233
2         b     3        2344

That mean ... For factor Id 1, I have 1500 records...and factor Id 2 I have same number of records.

For Factor Ids 1 &2 every values are same except "Factor Value".

When I join above table with some other tables to fetch data... FactorID 1 gives me quick results...but when I query for "2" ...the execution never ends.

This seems to be weird eror to me. Is it something related to row-lock ? Please helpme.